sometimes pc reboot

[Berk__]

first of all ı dont have very good english so sorry about that
my pc started rebooting itself.while playing gmes(LoL,Overwatch etc.)or browsing even while writing my computer password(after start windows 10 asks for pw)it tries to start again,%90 of the time screen is black(while case,fans everything is running)

PC SPECS:
Operating System: Windows 10 Home Single Language 64-bit (10.0, Build 14393)
Processor: Intel(R) Core(TM) i5-3470 CPU @ 3.20GHz (4 CPUs), ~3.2GHz
Memory: 8192MB RAM
Card name: NVIDIA GeForce GT 630
Display Memory: 6070 MB
Dedicated Memory: 1999 MB
Shared Memory: 4070 MB
Current Mode: 1920 x 1080 (32 bit) (60Hz)

there was no problem ntill last year or 1.5 years ago.(pc probbly 5 or 6.5 years old at the moment)
I NEED HELP PLS (

 

[darthvader30]

Which power supply are you using?

 

[Berk__]

Which power supply are you using?

casper 250 watt psu ı belive it is original psu didnt change anything

 

[darthvader30]

Your PSU is failing, you need at least a 450W PSU for this system. If you want a budget and good PSU Corsair VS550 will be good.