Imac screen flickering

HI There,
last week my 21 inch Imac screen started flicking randomly through out the day, sometimes really bad and Im worried that this computer is going to shut down on me....this computer in 2 years old and out of warranty, what shall I do?

By flickering do you mean the power is going on and off or is it just the display that's flickering? If it's the power, check the outlet it's plugged into and the AC line cord to the iMac. If it's the display that's flickering, that's something that you would likely have to get checked by Apple. An iMac is difficult to open up and trouble shoot.

hi there, it is just the display flickering, its not the power, so anyway just to be safe I decided to replug in my time capsule that was unplugged due to the modem cord not reaching the time capsule (i know lame excuse) but if I plug that in, the light is green does this automatically back up my computer?
please advise thanks...

As long as you haven't changed anything the TC should continue to backup as before. You might wish to take a look at the instructions for getting inside your iMac: iFixit: The free repair manual

good luck my first logic board did that before it died . the boards are expensive mine was still covered under warranty .