Internal clock

Ok so I wake up around 6:30 every day I don’t set a alarm or anything my it just the time set that I wake up and can’t go back to sleep. But it’s kind of concerning sometimes because I go to sleep around 4 AM and still wake up and not being able to go back to sleep, like even when I’m tired I just can’t sleep anymore. Sometimes the time changes too and it can be like at 4 AM for a couple of months I remember at some point I would wake up at 2 AM for a while. dose anyone else experiences this or know about it?