PC shuts down by itself while playing intense graphic games

[hinagiscout]

As i said my pc shuts down, happens faster with intense graphic games (like 10 mins), while with less demanding games can took like 4 hours to shut down.
I cleaned my pc, checked the temps while playing and everything seems normal.
I bought this pc like 4-5 years ago except for the graphic card that it was like 1 year ago, with that said ill leave my specs.
-Power supply: Thermaltake Smart SP-650P 80 PLUS Bronze, ATX, 120mm, 650W
-Graphic card: Nvidia Geforce Gtx 960
-Motherboard: ASRock H77M
-Cpu: QuadCore Intel Core i7-3770, 3900 MHz (39 x 100)
-Ram: Kingston HyperX KHX1600C9D3/4GX
-System: Windows 10 Pro 64 bits
-Hard drive: 2 Tb

https://prnt.sc/hc8nj2

https://prnt.sc/hc8nod

Some results from a system stability test, i hope this will help a bit

 

[hinagiscout]

MERGED QUESTION
Question from hinagiscout : "Pc shuts down without warning while gaming"

As the tittle says my pc shuts down randomly usually while gaming.
with High graphic games happens faster than with games less demanding.
I cleaned my pc, formated the system as well, checked the temps too and everything seems normal so i dont know what could it be.
Here are my specs:
-Operating System: Microsoft Windows 10 Pro 64-Bit
-Processor Description: Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz
-Ram: Kingston HyperX KHX1600C9D3/4GX (X2)
-Motherboard: ASRock H77M
-Bios: AMI EFI Version P1.30
-Total Hard Drive: 2.02TB
-Power Supply: Thermaltake Smart Standard 650W 80 PLUS Bronze ATX12V 2.3 Power Supply SP-650P
-Graphics Card: Nvidia Geforce Gtx 960

The pc was bought like 4-5 years ago, except for the graphic card that i bought it like 1 year ago.