sounds like maybe your power supply might be dying or your system is pulling more than that psu can handle. mine recently blew a capacitor with a loud bang and magic electronics smoke after a few months of odd problems with shutting down in the middle of an intensive game. i think the fan died about a year ago bc my temps had been higher than they used to and after it popped the side of the case by the psu was very warm. i came to find that my gpu upgrade pushed my power draw to 450w when my psu was only rated for 530w and not 750w like i thought i remembered. makes sense it was pushed to it's limit. maybe recheck your power requirements with an online psu calc and compare to your psu rating. and also look to see if its fan is still running and not clogged up with dust.