I totally experience that, too. It can be really unnerving. I seem to have a difficulty chaining together the events of my day into a story; instead, it seems like parts of the day happened a very long time ago or not at all.

At least once a day, someone else asks me where I've been or what I'm looking at. Usually, this brings me to the present moment. I'm not aware of staring off into space in the moments before that. I'm guessing my dissociation happens even more often than I'm aware of.