Yeah, I'm not sure if mine was from sleep deprivation or not, it was just my best guess. And now I can't remember if I had got enough sleep the night before or not. I posted a question about it at the time, hoping some experienced meditator would be able to tell me something about it, but nobody did. It hasn't happened to me since then.

Anyway, you're noticing a lot of the weird states of consciousness that happen when you're falling asleep, which most people usually aren't aware of. That's good - keep it up!