Sleep

Would someone explain this, please...

I can go to bed at night, sleep for many hours, dream lengthy dreams, and when I find myself waking up I think it's close to sunrise and therefore it's almost time to get up. When I turn over to look at the clock on my phone, it's usually been (at the most) about three hours since I went to bed.

This has happened more than once. As one would expect, the idea is worse this time of year because of the later sunrises.