Just two ideas:
1) how much do you exercise?
2) what do you eat?
I have found out that exercise and food have a
huge impact on the amount and timing of sleep I need. Maybe you're sensitive to that too.
I recommend a 30days trial: eat no dairy, no meat, no sugar and drink no coffee for 30 days, and move in a relaxed manner (going for a walk is enough, doesn't need to be real exercise)
outside for two hours a day. I bet your sleep pattern will improve
(I'm not telling you to do that forever, it's just a trial to see what happens)