[SOLVED] PC instantly reboots when playing games

[Retzelio]

I have this 8 month prebuilt pc, and it was working fine until now, when playing games that has high graphics like GTA V, League, AC: Syndicate, Apex, etc. it suddenly turns off and reboots, I don't know what might have caused this, because it was not an issue before, I tried setting the pc fans to its maximum but nothing works, and I have little to no knowledge when it comes to fixing computers, when I try to check its temperatures using a stress test, it also reboots, so I don't know how hot cpu or gpu gets when playing, as I have said this was not an issue before, so why does it happen now?
BELOW ARE THE SPECIFICATIONS:

CPU: AMD Ryzen 5 2600 Six-Core Processor 3.40 GHz
GPU: Radeon RX 570
MOTHERBOARD : BIOSTAR A320MH
RAM: DDR4 1 Module 8GB
PSU: zalman zm700tx

 

[JohnBonhamsGhost]

use an OSD while playing or stressing to watch how the temperatures react.
setup Afterburner & RTSS and you can set it to show on your taskbar while windowed and on-screen while in full screen.

you don't mention your CPU cooler & how it's setup
or your case & it's cooling setup.

 

[Retzelio]

https://imgur.com/a/l60ZbPc

this is how it looks, also the moment I click "Stress Test" it literally turn off, its like a shutdown button, it won't even give the OSD to update its info