If the PC was running before, it only helps to reset the Mobo Bios. If that doesn't work, a 2-3 digit code should appear on the motherboard with which you can isolate the error. Finally, I would remove the graphics card, remove the dust and reinstall it and, if necessary, change the battery on the board when it is 5-6 years old.
I also had a problem like this during my rebuilding, which I was able to solve with Gigabyte Support. I had to loosen the cooler from the CPU and it has been running ever since.
