Have you ever been walking through your house, merrily doing your stuff, when you just suddenly stop, cock your head slightly to one side, and realize you have absolutely no idea what you were about to do? You stand there for a few seconds, and you can't even think of the fact that you don't know, you just go blank, like someone kicked out the plug to your brain for a few seconds? Then, it just comes back into focus, and off you go?
I just did that on the way to my dresser for a shirt. *shrug*