Scramble/Pixelated then flickering screen.

Hi everyone - not sure what to make of this. Screen scrambles/pixelates, then flickers and freezes. Computer seems to run fine. No hard drive clicking or any other unusual sounds. Since it's the screen I'm thinking it could be a connection or the graphics card. I understand computers, but I'm by no means an expert. I'm looking for opinions on what anyone thinks this could be. I do have an image of the problem, but I'm at work and apparently our internet blocking software won't let me attach the image.