My computer has recently started acting up and been doing a couple of weird things. The first thing that happened was that during games the GPU temperature would reach about 85C then the screen would go blank and the fans would spin at 100% until I turned off the computer and switched it back on. After this happening a couple of times the fan stopped spinning at 100% and instead the graphics card seemed to just stop doing anything; I believe I was getting blue screens but my monitor wouldn't show anything until I restarted. In heaven benchmark my graphics card would get to around 85C then producing a load of artifacts before reaching 90C (Artifacts got worse as temperature went up) and crashing like I described above. My graphics card is an EVGA 660GTX SC.
Then after a couple of times of that happening I would switch off my computer and let it power down, try to switch it back on and there would be a 2-3 second delay between pressing the power button and the computer turning on. If I waited 5-10 seconds after powering down then there wasn't this delay. This also causes problems when I try to restart my computer as it restarts with no video and loads into windows with no video output the whole time.
I had been thinking it was my graphics card so I swapped it out for an old HD5750 that was lying around but the problem on restart still happens. I don't get the same problem of the GPU stopping working but I think this is due to the 5750 using less power.
I have also tried testing my 660 in another computer to see if the problem could be reproduced. I ran heaven benchmark and sure enough the temperature got to around 85C and started producing a load of artifacts and then eventually crashed. this time after the crash the gpu's fan stopped spinning altogether.
I'm really not sure if both my power supply and graphics card are on the way out or if this problem on restart is some sort of safety measure caused by the graphics card repeatedly dying. I have tried resetting bios settings with no improvement.