Custom-built gaming computer (i7 4790k, GTX 970, 16GB RAM, Corsair 750W PSU, Asus Monitor 144Hz)
restarts when playing modern games such as Fortnite, CS:GO Assassin's Creed Black Flag, Tekken 7 etc
The whole rig is 2 1/2 years old
I cleaned the dust out of it and the PSU
I tested the PSU...