Consider eating patterns: do you eat when you get up? If so, defer to the time you'd rather rise. (Also: when do you last eat before going to sleep? Can that be shifted later?)

Is there light/noise/roommate/etc. which triggers the early-wake, which you could mitigate?

Do you know if you snore or have sleep apnea? (You could go to a sleep-specialist for relevant tests, one of which is a finger-mounted blood-oxygen meter you take home.)