Getting restarted automatically AMD,ASUS,Sapphire GPU

[AniAM]

My system getting restarted automatically now and then. The temperature is normal. 40C - 45C. Suppose I'm browsing net or listening songs or watching movies,the machine getting restarted from it's own. Any reason? Quite a baffling situation I'm facing. HELP NEEDED BADLY.

 

[Suztera]

What is your full pc build?
What are your idle and max temps for the cpu?

 

[AniAM]

What is your full pc build?
What are your idle and max temps for the cpu?

Build-
*AMD Fx 8320
*ASUS M5A97 R 2.0
*Sapphire R7 250 1Gb GDDR5
*1 TB HDD WD Caviar Blue

Temp. -
Simple browsing,songs,movies- 42C to 48C
Gaming (BF3,BF4,MW3,MW2)- 58C to 67C

 

[Suztera]

Did you do any overclocking to the cpu or/and gpu?
Temps for cpu is higher than expected. What cpu cooler are you using?
What is your max ambient temperature?

 

[AniAM]

Did you do any overclocking to the cpu or/and gpu?
Temps for cpu is higher than expected. What cpu cooler are you using?
What is your max ambient temperature?

I did not OC the CPU & GPU and never will.
Using the stock cooler (bad,no doubt)
There are two famous words. Calcutta Summer. It does currently have 36C max, 28c min. When it comes to the highest,it becomes around 42C. NEED A SOLUTION.