My cpu is not turning on

So 3 days ago it was working fine till next day, it wasn't powering up in the morning. It finally turned on after a few tries than it worked fine for the entire day, the next day same problem it wasn't turning on and i tried few hrs later it finally turned on and worked fine on that day. 3rd day it wasn't powering on after several tries idk whats the problem its the 4th day it still wont turn here also rainy season and usual power cuts happen idk if that's the case but i do have a ups. Can anyone tell me the possible cause and if i can check on it myself