What is your power supply , Brand , watts and model how long have you had it. If you power down and unplug then you can recheck the power connections and make sure that the card is seated all the way into the slot. How long hve you had the video card and what brand and model.
My power supply is 1000 watt , cooler master silent pro. I've had the card for about a year maybe a bit less. The manufacturer of the graphics card is Sparkle.