Question PC takes a while to start again after turning it off and restarts under high GPU load

Dec 26, 2020
About a year ago my PC started taking a lot of time (from 15 minutes to 3-4 hours, even if not always) to turn on again after I turned it off (while it had no problems with restarts). Since then I changed my mobo, cpu, ram and gpu and I did a fresh installation of windows 10.
Now, after I upgraded my cpu, mobo and ram and I did the fresh installation of windows, I noticed, using teamviewer, that I have to disable desktop hide setting and turn it on again in order to see the desktop, (while if I press keys or click randomly it receives the input) and now, (expecially after I tryed to overclock the GPU using msi afterburn, even if I disabled the overclock and unistalled it), my PC restarts when GPU is under high load (it takes from 1 second to 2-3 hours to restart), and sometimes when it restarts, there is no video signal, while other time my GPU is not seen and it runs with CPU graphic card (even if the HDMI cable in connected to the 1660). Another thing I can say is that for a couple of weeks after the fresh installation of windows it stopped having problem to boot after I turned it off.
What could the problem be? I was thinking about the PSU, which is 5 years old, but I'm not sure.

My system:
CPU: intel i5 10500
RAM: Corsair CMK16GX4M2B3000C15 2x8GB 3000MHz
MOBO: Asus TUF gaming b460-plus
GPU: Gigabyte GeForce gtx 1660 super OC
PSU: Antec True Power TP650C 80 plus gold - 650 Watt (5 years old)