No matter whether i go to sleep at 9:30, 10, or 11, i wake up at ~4 am, and it is a feeling of "i'm done sleeping." what to do? thanks.

Sleep: How much?: Looking at your age and comparing my own experience as an aging man your question made me smile. As we age we often do need less sleep. The first question i would have as your doctor would be if you feel depressed or chronically fatigued. If you do not feel rested when you awaken then there may be more of a concern. But, if you are getting a good six hours of sleep, this may be all you need.