NAD but same (and it started around your age in me too). I do believe I have Delayed Sleep Phase Syndrome where my ideal sleeping time is around 2-4AM when I would like to go to sleep at midnight at the latest. If I force myself to go to sleep at midnight (and I have tried this for weeks on end) I will either flat out still stay awake until around 2-4AM or I will fall asleep but it will be a restless/not deep sleep where I wake up several times for 'no reason' the entire rest of the night which is even worse than just going to bed at 2AM. I am obviously not a doctor but what you describe does sound like DSPS could be something for you to look in to. But I do wish the best to you and you're right for looking in to this now. When I was younger I brushed it off because even getting 4-5 hours a night in school was seemingly A-OK for me. I didn't have horrible day time drowsiness and I did well in school still. But in my mid twenties that stopped being the case and it did start to really affect me.

For others - I am looking in to getting diagnosed but right now I can't work due to chronic illnesses acting up and my mental health tanking so I am fortunate I can stick to an 'odd' sleep pattern for now. Before anyone chews me out for not getting tested, I know! lol I have been trying to book a sleep study for a year+ now but I keep getting diagnosed with new crap and put on new meds etc. and I can't keep my appointments as per the instructions of the sleep clinic doctors.