Full PC specs, including make and model of PSU..
Install aida64, check the temperatures in particular of the CPU, there is a stress test in the same program, you can run it separately, for memory on the processor, and look at the temperatures. the first tick does not load the processor much, the second one additionally loads, you can immediately put 3 ticks on the processor, if the temperatures are normal for your processor, wait for at least 15 minutes for a while, if the processor starts to reset frequencies due to overheating, the problem is clearly cooling. Then you can run a stress test for RAM, the fourth tick in the same program, do not run the stress test all at once! it is necessary to identify the problem separately, or the processor RAM pours and gives errors. Perhaps the connectors in the motherboard are simply not fully connected, or RAM is not fully inserted. Here you need to check as I said separately)) For RAM, I recommend using the testmem5 utility. You can also check the hard drive using crystaldiskinfo.