What exactly were the max temperatures of the CPU and of the GPU you measured?
Check the fans, clean the inside. To be sure about the heat, run with the side cover off and a fan blowing into the for extra cooling.
Undo all overclocking.
See if the BIOS needs to be updated.

Anyway, this looks like a hardware issue. Things to replace, as an experiment, if the above doesn't help: fans and heat paste, PSU, graphic card, motherboard, RAM.