Thanks for the clarification.
In this case, it is clear that there is a hardware problem with your PC. However, it is not clear whether the problem is actually with the GPU, as it could also be a problem with the motherboard, CPU, or power supply.
You have already checked for problems with the RAM and disk. Unfortunately, there is no reliable software to test the other parts.
I suggest you consult a technician you trust or the manufacturer's authorized support.
Sorry for the bad news.
If you have any questions, don't hesitate to ask. Click on the "Reply" button below my reply.