i have the exact same issue, i'm thinking of changing my psu as well, as about a year and a half ago this started to happen, and now everytime i turn it on my cpu fans spin up and the usage is all over the place and i think it just happened as soon as i started overclocking, and now well its all messed up. So i would recommend changing out the psu otherwise its going to get worse like mine, now it just restarts randomly and cpu usage is high, i legit made a forum post about it yesterday. good luck. also try to use the hdmi port or other video out directly from the motherboard and take out the gpu just to make sure its not the gpu, if it still happens well its most likely to be the psu. Also what is you psu, mine s the corasir vs450, i've heard that its a bit unreliable so yeah make sure to search up issues about your psu and if other people are experiencing the same thing then its most likely the psu.
-Yash