Is all sin premeditated?
I was intrigued by your question. I am not sure what you exactly mean by premeditated and what boundaries to go by, but in the Bible, there are sins mentioned that people don't realize what they are doing. There are also other sins where people just were not given enough information and sinned. Here are some examples in Scripture"
"Speak to the sons of Israel, saying, 'If a person sins unintentionally in any of the things which the LORD has commanded not to be done, and commits any of them" (Leviticus 4:2).
"When a leader sins and unintentionally does any one of all the things which the LORD his God has commanded not to be done, and he becomes guilty, if his sin which he has committed is made known to him, he shall bring for his offering a goat, a male without defect" (Leviticus 4:22-23).
"If a person acts unfaithfully and sins unintentionally against the LORD'S holy things, then he shall bring his guilt offering to the LORD: a ram without defect from the flock, according to your valuation in silver by shekels, in terms of the shekel of the sanctuary, for a guilt offering. ... Now if a person sins and does any of the things which the LORD has commanded not to be done, though he was unaware, still he is guilty and shall bear his punishment. "He is then to bring to the priest a ram without defect from the flock, according to your valuation, for a guilt offering. So the priest shall make atonement for him concerning his error in which he sinned unintentionally and did not know it, and it will be forgiven him" (Leviticus 5:15, 17-18).
"But if a man eats a holy gift unintentionally, then he shall add to it a fifth of it and shall give the holy gift to the priest." (Leviticus 22:14).
"But when you unwittingly fail and do not observe all these commandments, which the LORD has spoken to Moses, … then it shall be, if it is done unintentionally, without the knowledge of the congregation, that all the congregation shall offer one bull for a burnt offering, as a soothing aroma to the LORD, with its grain offering and its drink offering, according to the ordinance, and one male goat for a sin offering. ... The priest shall make atonement before the LORD for the person who goes astray when he sins unintentionally, making atonement for him that he may be forgiven. You shall have one law for him who does anything unintentionally, for him who is native among the sons of Israel and for the alien who sojourns among them. Also if one person sins unintentionally, then he shall offer a one year old female goat for a sin offering" (Numbers 15:22,24,27-29).
"Then you shall select for yourselves cities to be your cities of refuge, that the manslayer who has killed any person unintentionally may flee there. ... These six cities shall be for refuge for the sons of Israel, and for the alien and for the sojourner among them; that anyone who kills a person unintentionally may flee there" (Numbers 35:11,15).
"That a manslayer might flee there, who unintentionally slew his neighbor without having enmity toward him in time past; and by fleeing to one of these cities he might live" (Deuteronomy 4:42).
"Now this is the case of the manslayer who may flee there and live: when he kills his friend unintentionally, not hating him previously -- as when a man goes into the forest with his friend to cut wood, and his hand swings the axe to cut down the tree, and the iron head slips off the handle and strikes his friend so that he dies -- he may flee to one of these cities and live" (Deuteronomy 19:4-5).
"That the manslayer who kills any person unintentionally, without premeditation, may flee there, and they shall become your refuge from the avenger of blood. … These were the appointed cities for all the sons of Israel and for the stranger who sojourns among them, that whoever kills any person unintentionally may flee there, and not die by the hand of the avenger of blood until he stands before the congregation" (Joshua 20:3,9).
Notice Leviticus 22:14. If a person eats a holy gift accidentally it is a sin. I could accidentally be given food without knowing where it came from and sin; therefore the sin was not premeditated, my intention was to just eat some food.
People who accidentally killed someone or had no premeditation beforehand could flee to cities to be safe. Deuteronomy 19:4-5 doesn't make it unclear whether an accidental death is a sin, but a person still held responsible.
The list shows that, one way or another, sin is not always premeditated. It's always a choice, but that choice might be rashly made without forethought. For example
"And when they came to Nachon's threshing floor, Uzzah put out his hand to the ark of God and took hold of it, for the oxen stumbled. Then the anger of the Lord was aroused against Uzzah, and God struck him there for his error; and he died there by the ark of God" (II Samuel 6:6-7).
Did Uzzah know the commands of the Lord? Most likely, but with just a mere reaction he made a quick response that cost him his life. He sinned. Was he planning on sinning? The answer is "no," he had a split second to decide, he just reacted and it was the wrong choice.
Another story to note is about a prophet who lost his life when he believed someone's lie:
"Then the king said to the man of God, "Come home with me and refresh yourself, and I will give you a reward." But the man of God said to the king, "If you were to give me half your house I would not go with you, nor would I eat bread or drink water in this place. "For so it was commanded me by the word of the LORD, saying, 'You shall eat no bread, nor drink water, nor return by the way which you came.'" So he went another way and did not return by the way which he came to Bethel. Now an old prophet was living in Bethel; and his sons came and told him all the deeds which the man of God had done that day in Bethel; the words which he had spoken to the king, these also they related to their father. Their father said to them, "Which way did he go?" Now his sons had seen the way which the man of God who came from Judah had gone. Then he said to his sons, "Saddle the donkey for me." So they saddled the donkey for him and he rode away on it. So he went after the man of God and found him sitting under an oak; and he said to him, "Are you the man of God who came from Judah?" And he said, "I am." Then he said to him, "Come home with me and eat bread." He said, "I cannot return with you, nor go with you, nor will I eat bread or drink water with you in this place. "For a command came to me by the word of the LORD, 'You shall eat no bread, nor drink water there; do not return by going the way which you came.'" He said to him, "I also am a prophet like you, and an angel spoke to me by the word of the LORD, saying, 'Bring him back with you to your house, that he may eat bread and drink water.'" But he lied to him. So he went back with him, and ate bread in his house and drank water. Now it came about, as they were sitting down at the table, that the word of the LORD came to the prophet who had brought him back; and he cried to the man of God who came from Judah, saying, "Thus says the LORD, 'Because you have disobeyed the command of the LORD, and have not observed the commandment which the LORD your God commanded you, but have returned and eaten bread and drunk water in the place of which He said to you, "Eat no bread and drink no water"; your body shall not come to the grave of your fathers.'" It came about after he had eaten bread and after he had drunk, that he saddled the donkey for him, for the prophet whom he had brought back. Now when he had gone, a lion met him on the way and killed him, and his body was thrown on the road, with the donkey standing beside it; the lion also was standing beside the body" (I King 13:7-24)
Notice that the prophet had been commanded by God not to eat, drink or go back the same way home, but then another prophet tells him otherwise -- to eat and drink -- and he believes the other prophet. The consequence is that he sinned even though he was deceived. Though he thought he was doing the right thing, it cost him his life. His intention was to follow God and not sin, but he failed to ask God if what was said was true.
Hope this answers your question from a couple of different angles.