My brain is trying to kill me

I generally wake up for no apparent reason around 5 a.m. I go back to sleep, but not deeply asleep, so it' definitely affecting how rested I feel (which is not at all!) So today I had to get up at 5 to go into work and conduct doctor surveys. I'm thinking, this is cool, because I'll sleep soundly until 5, when I tend to wake up anyway. But noooo. Instead I wake up at 4 for no apparent reason and get the same dozey sleep for the last hour that I get every day. What the heck???