My pc going to sleep with out warning

[attaribha]

Hello,
sir i have fallan problem
my dell seystem GX780 problem that is going to sleep with out any warning and restart emegiatly plz tell me solution

 

[rgd1101]

it an old PC. could be overheat, psu failing, or something else.

 

[MC_K7]

If the PC restarts, it's not going to sleep then.

 

[dextermat]

+1 it an old PC. could be overheat, psu failing, or something else.
+1 If the PC restarts, it's not going to sleep then.