My PC turns off suddenly

My PC turns off suddenly and randomly while playing. Sometimes my CPU heats up to around 70°C but I don’t think that’s the problem, since there have been occasions where it turns off without being really heated. I did a stress test of power and CPU for 15 minutes and it didn’t shut down in none of them, but it reached 90°C temperature in the power one.

This are my specs:

Motherboard: Gigabyte AB350M-Gaming 3 CPU: AMD Ryzen 7 2700 GPU: NVIDIA GeForce RTX 3060Ti RAM: 2x8gb Asgard 3200mhz PSU: Coolermaster 500w 80Plus

Please if somebody can help me and give me your opinions!