Question PC crashes randomly

Oct 19, 2020
A year ago I assembled my first pc. It wasn't easy and it didn't want to start at the beginning but after dissembling and assembling again it started and since then the only problem I had was, as title says, random shut off. Or not exactly shut offs.

After starting I can use it for a whole day without any issues. I don't turn it off, only suspend to memory. On the next day I wake it up and use it for a whole day. Once a week or after a huge update I make a full restart.

But from time to time, after waking up, it freezes. Sometimes it freezes everything and I can see my screen until I reset it, but mostly I don't see anything because my monitor turns off immediately (monitor's led changes from green to orange, sometimes with information that there is no signal). Sometimes it takes time and while listening to something I hear stutter (from radio or youtube). There are months without problems and then for a weeks it would be after each wake up.

It happens only after waking up and after starting. But recently it went deeper and turns off even after an hour of being on.

I've cleaned it thoroughly today (disassembled and assembled to make sure I didn't miss anything). After reconnecting I started it, wen through starting screen of MB, then grub options and then I've waited watching at black screen and eventually loosing a signal (monitor turned off).

I'm not very technical (assembling it was a real challenge) and I don't even know what it might be. I guess it's maybe a graphic card loosing signal but would it freeze a whole system? Maybe a system? I've installed it 3 times already.

I have cpu and gpu temperatures widget on the bar so I'm monitoring it all the time and besides playing games and rendering when they go up significantly it seems everything is fine (and even then it's not overheating). It never happened during game play.

System: Manjaro + Plasma KDE

Besides those parts I have 3 additional fans.