I'm the same way. I think a lot of it, for me, is a sleep disorder that messes with my circadian rhythm. No matter how sleep-deprived I am, around 10:00 at night, my brain and body are like, "Hey! We're awake! Let's do stuff!" It's very annoying because it would be far more useful to have that energy and brain power during work hours instead of feeling half-asleep all day, and I'd be a lot less sleep deprived if I could actually sleep at night.