I know what you're talking about. It'll happen to me sometimes, too. Basically just means that your body is burning off the THC metabolites in your system during your sleep and when you wake up there's enough in your bloodstream at the time to produce an effect. I call it a stoneover for both that, and when you smoke before you go to sleep and wake up high. I don't like it, but I do. Mellows me out, but sorta too much.