I'm surprised no one has mentioned sugar or carbs late at night. I sleep great now that I've lost weight for the most part, but if I eat too much sweet stuff right before bed, I'll go to sleep OK but wake up two or three hours later. It's like I rebound off the carbs. I sometimes will also have a headache in the morning from carbs--almost like a hangover.
I have always had to be careful with caffeine late in the day, even when I was much younger.
Benadryl works fine for me, but 5HTP makes me feel very strange, so I stay away from that one.
Of course, from time to time I'll have too much stress going on, and that wakes me up. Don't you just love that--it's 4 a.m. and you're worrying about things you can do absolutely nothing about at that hour.
Or you have to get up early for some kind of big thing the next day, so you wake up every hour to make sure the alarm clock is still set and hasn't gone off. ARRRR!
Jay