iMac A1312 2011 restarting

[mushr00m]

This iMac is restarting sometimes and I am getting this error message

Any advice on what could be the issue related to this?

tried to upload but says too large files

Link of the images ->

https://imgur.com/a/fHcnprf

 

[2informaticos]

Probably CPU issue.

Any problem appears running GPU stress software?
See if ASD reports any error.

 

[mushr00m]

Sometimes using Heaven benchmark it restarts

Important to mention that I replaced original GPU with the K1100 since it had problem with original GPU

 

[mushr00m]

Assembled the OS and EFI bootable ASD drive related to the iMac A1312

Problems with it:
It open the EFI version but freezes as soon as I click "TEST"
it tried to load the OS version but gets stuck


IMPORTANT to mention
if it was turn off for some hours and I turn on it works for sometimes. Looks like as soon as it gets some kind of hot then it restart and keep restarting as soon as log in the system.... That's the kind of error and the message is the one I already sent through imgur

 

[2informaticos]

You should discard graphics card first.