card randomly stops

Yesterday I had an incident where my screen just went black and the monitor went on sleep mode and clicking keys/pressing the mouse just woke it up to a black screen. After looking through my case to see if anything was wrong I noticed my gpu (Radeon HD 6750) was unpowered. I turned the power off and all and tried inserting it into another PCI slot but that had no effect. The fan wasn't spinning and there was still no display on the monitor. But then I put the card back in the next morning and now the display is up and working again. Does anyone might know why this is? My drivers are up to date and all. Thanks

I'm not sure about the fan stopping, but my 7850 still crashes my display even on the latest 12.8 drivers.