PC won't start

[PotatoComputerMaster]

[video="https://m.youtube.com/watch?v=swLStlE_rEY"][/video]The PC will start but the start up light and power supply are the only things turning on. When turned on and all the things happen it turns off after sometime, it used to be able to turn back on after all these happen if I unplug it for a while and then plug back in and wait a while when it turns on them everything else powers up after a while.

before it had an A2 lighting up on the mobo and a black screen

 

[Fezodar]

The PC will start but the start up light and power supply are the only things turning on. When turned on and all the things happen it turns off after sometime, it used to be able to turn back on after all these happen if I unplug it for a while and then plug back in and wait a while when it turns on them everything else powers up after a while.

before it had an A2 lighting up on the mobo and a black screen

 

[Fezodar]

When was the last time you have changed your thermal compound and cleaned inside your case?
Have you tried using a spare psu to test your PC?

 

[PotatoComputerMaster]

When was the last time you have changed your thermal compound and cleaned inside your case?

4 months ago and this a video of the pc.
https://m.youtube.com/watch?v=swLStlE_rEY