I've noticed that I often wake about an hour or two before I should get up. When I awake, I often feel pretty energetic but I go back to sleep because of course, I have a couple more hours awaiting me. Then when I wake up the second time, I can feel "dead" or really tired. Does anyone know why this occurs? Does this happen to anyone else? And often when I wake up early, I haven't gotten enough sleep (for example, 5 hours) so I don't think it's an issue of oversleeping. Well thanks.