MBP 2012 15“ wouldn’t start and freeze after a couple minutes

Not sure if I’m in the right subreddit, but I run on my MBP open core with Sonoma. Works perfect usually. After one week not using it I wanted to start it and it wouldn’t start. I tried to start it multiple times and eventually it did and I could log in normally. But then the fans went up and when they went down the whole thing froze. So I rebooted it. This happened like three times. Then when I rebooted it a forth time there was one piep. After that I unplugged the battery put out the RAM and put only one inside (4 gb now) and turned it on and now there is no more the classic Apple boot sound just white screen and it booted. Now running the opencore update 1.2. (?)

Does someone knows what wrong? Maybe it’s helpful to know that I played last week on the MacBook openemu but just a gba game.

Thanks in advance lovely redditers.