Weird black screen problem, help please.

Hello everyone,

I'm here because my ps3 is acting weird.
I can start my ps3 and play games without problems,
but once I shut it down I can't start it again for the next 30 min.
I can still start the playstation and the green light is showing (only green) but i'm just getting a black screen and can't connect my crontroller.
I tried to boot in safe mode and I hear the beebs, but i'm still just having a black screen.
If I wait like half an hour, maybe longer it will work again until I shut it down again.

Anybody knows what the problem is?

Thanks a lot !