Question PC resets randomly without warning while gaming

Jan 31, 2020
Hi, like a month ago my pc started to randomly resets while gaming, it resets like 5 times in all this time and it's very random. Somedays i can play without any problem. Like a year ago i changed my gpu (sapphire radeon 7870) because it starts malfuntioning, I bought a Sapphire Radeon rx580 pulse, and since a month, give or take, my pc randomly resets without BSOD(disabled automatic restart on system failure) or any warning whatsover(checked on the event viewer, it just says the generic critical error: The system has rebooted without cleanly shutting down first ), I think may be my psu is starting to give up, I bought it 8 years ago. My specs are sabertooth 990fx r2, cpu amd fx6300, RAM 2x8gb g-skill sniper, drives 1 samsung ssd 250gb(windows installation), 1 samsung ssd500gb and 1 hdd westerndigital black 4tb, my psu is a thermaltake smart m750w. I tested and there's no overheating, while gaming my gpu reaches 70°C at most, and the cpu like 60°C.
Any thoughts?

PS: Forgot to mention that one time while gaming my monitor went to sleep, my pc was still running but have no audio, there was a red light on the motherboard when that happened and couldn't reset the pc by any means, I had to turn off the psu and on again to start the computer.