Pc not booting sometimes

[Csmith339]

Sometimes when i turn my computer on it gets stuck at the lenovo screen and wont boot. Everything inside my case is running and working but it just wont boot. Eventually ill turn it off and on and after the second or third try it will boot. What could be the problem here and how can i fix it ?

 

[Csmith339]

this just started happening after upgrading cpu cooler to the cooler master evo 212. could this make a difference?