computer shutdown automatically after a while

[mamnoon12]

mother board: gigabyte
processor: i5 4430
ram: 8gb 1600mhz
gpu: gtx 750ti sc
powersupply: 450watts some local brand


my pc shutsdown after about 30mins of booting and then turns back on automatically i have been having this problem for like a week now and cant come to a decision any one can help.

 

[Dark Lord of Tech]

450 watts "some local brand"

Not a good sign of a reliable power source.

 

[mamnoon12]

450 watts "some local brand"

Not a good sign of a reliable power source.

but the thing is it has been working for over 2 years now and i have checked the power out put of it in hw and the power is ok
13v 3.3v 5v and cpu and gpu temps are also ok. help plz

 

[Dark Lord of Tech]

If it's not a thermal issue , then it's most likely the PSU.

 

[mamnoon12]

If it's not a thermal issue , then it's most likely the PSU.

but the thing is that is it was a psu issue then why are the watts or volts ok and it cant be a thermal issue i have applied a new thermal paste on the cpu and all the temps are great not just ok i think tomorrow i will try swapping the psu and check if still the problem occurs and do you think the motherboard could be at fault and so help me how to check if thats the case.