B850M Pro RS Boot issues

Hello
My B850M Pro RS WiFi does not boot (POST) anymore.
The system:
- MB: B850M Pro RS WiFi
- CPU: AMD Ryzen 7 9700X
- RAM: G.Skill Flare X5 64GB (2x32GB) Kit DDR5-6000 CL28
- SSD: Samsung 990 Pro 4TB
- PSU: Corsair RM650e

I bought the components some 3 months ago and everything worked extremely well -- until today.
When I turn on the PC this morning, the fans spin, the red and yellow LEDs (CPU and RAM error) are on and that's it, no graphics output, no caps-lock on the keyboard, no nothing -- at least most of the time.
Sometimes, red and yellow turn off, green and white LEDs flash shortly and the ASRock logo is on the screen -- and stays there, nothing more.
Two times even the boot process started but when I was prompted for my boot password, no keys strokes where registered and the system seemed stuck.
A few times red and yellow were on for about 1min or so, then shortly green and white but then just red and yellow again.
To summarize, it is not 100% consistent, but the red and yellow LEDs turn "reliably" on, the keyboard is not functional, and there is no graphic output or only the ASRock logo.

I've tried to flash BIOS v3.30, nothing changed, same with v3.20 and v3.25.
I've tried only one RAM bar (once for each bar), I've changed the mounting pressure on the CPU, I've let it idle for about 1h with red/yellow LEDs on, nothing worked so far.
Do you need more information?

I see a lot of topics with similar issues.
Is there anything I could try in addition?
Regards, snygg

One additional thing, maybe unrelated, but 1 or 2 days ago the WiFi suddenly did not work anymore. I rebooted, did not work in Windows, not in Linux, not in USB-Sticks. After I unplugged the power from the PC for a few hours and WiFi was available again -- as if nothing happened.