Your story (and others in the reply) sound a lot like experiences of people taking Ambien (Zolpidem) - sometime, they "wake up" in the middle of being awake, and more - sometimes, they do things (like eat, drive, email, etc.) without any recollection. Often, just as sharp as when they are really awake, but sometimes, very weirdly (people driving naked, stuff like that).

To me, that (and experiments of Gazanigga etc) indicate that Jaynes was onto something with the "bicameral mind" theory, as crazy as it sounds.