What is the word for doing an act and not knowing you're doing it until its done?

Like standing in one area of a room and then the next thing you know you’re across the room stuck in a weird fighting stance position, Because you were taking something from someone and you didn't realize you were doing this until they called your name. Kind of feels like you were going through a tunnel. Like unintentional tunnel vision.

This might be called automatism:-

1. the state or quality of being automatic; mechanical or involuntary action
2. (Law) law philosophy the explanation of an action, or of action in general, as determined by the physiological states of the individual, admissible in law as a defence when the physiological state is involuntary, as in sleepwalking [Collins English Dictionary]

explained further here:-

An involuntary act such as sleepwalking that is performed in a state of unconsciousness. The subject does not act voluntarily and is not fully aware of his or her actions while in a state of automatism. Automatism has been used as a defense to show that a defendant lacked the requisite mental state for the commission of a crime. A defense based on automatism asserts that there was no act in the legal sense because at the time of the alleged crime, the defendant had no psychic awareness or volition. Some American jurisdictions have recognized automatism as a complete, Affirmative Defense to most criminal charges. An Insanity Defense, by comparison, asserts that the accused possessed psychic awareness or volition, but at the time of the offense, the accused possessed a mental disorder or defect that caused them to commit the offense or prevented them from understanding the wrongness of the offense. [West's Encyclopedia of Law]

Fugue state, sometimes called dissociation, describes a psychotic state where this happens, as opposed to the sort of zoning out that happens when you're commuting, for instance, and realize you've gotten home without really recalling the intervening trip.