Question Why does my computer suddenly goes like LOW PC af,

[Matt050514]

My computer suddenly goes for like 60 to 90 FPS at fortnite but i was having normally 144+, my computer sometimes when i want to turn him on, he does this (turns on, turns off, turns on, turns off, turns on, turns off..., until i take out the source cabel little bit or fully) so can it be a bad source or something like that like motherboard,...

 

[Dj0gany]

can you list the full pc specs includin mobo,and psu