Question PC Crashing and won't reboot immediately

Dec 22, 2020

Operating System
Windows 10 Home 64-bit

Intel Core i7 6700K @ 4.00GHz

16,0GB Dual-Channel HYPERX @ 1333MHz

MSI Z170A GAMING M7 (MS-7976) (U3E1)

4095MB NVIDIA GeForce GTX 1080

Power Supply
Cooler Master G750M


So basically my pc crashes without a blue screen sometimes. Screens go all black and it reboots. Now it won't reboot immediately and the status LED on my motherboard says: 00. Now I have to turn off the power and wait for sometimes 5 to 45 min until it will turn on again. If I go into the BIOS and press exit (-> reboot) I got the same waiting problem again. Even after a normal shutdown it sometimes happens. I installed programs which monitor the heat (degrees of the components) and log them all the time. But still one seccond before a crash they are fine (not too hot). I even tried resetting my pc and this didn't help at all. I disabled all overclocking things and didn't help either. Its weird that my pc can handle games like rdr2 almost max settings and won't crash and then it crashes when I am playing Lego Harry Potter?! (On some days it crashes on rdr2 too, but on the most days it can handle it.) I tried as using as few programs as possible but it is still crashing. For example I am writting this in my browser right now and when I am not playing any game my pc won't crash. In the last few days it startet crashing while playing Fall Guys and watching a video on the browser (this happened a few times now). I got two monitors by the way, but using only one doesn't help at all. I even cleaned my whole pc from dust and the fans seem to work fine.
Another problem which might be corresponding, is that when I start my pc the time is often not right. Like it's still the same one from last evening and I have to sync it at the start.

I don't know what to do now, maybe someone of you can help me.

(sorry for spelling and grammatical mistakes)