Your GPU is likely bad.Do these diagnoses.
1.please check that the dvi or hdmi cable is properly connected.
2.Try reseating your gpu.
3.Try uninstalling the drivers.Take out your gpu and use onboard video to uninstall drivers then put your gpu in and reinstall the gpu driver.you dont have to take out the gpu if your cpu doesnt have onboard video.if you have an intel cpu you will have onboard video.
4.try plugging your gpu to another monitor or hook it up to your tv with hdmi and then try if the issue goes away then your monitor was bad
if none of these work your gpu is likely bad and you have to RMA the card. good luck!