To Repair my panasonic tv sony?

>My Panasonic tv is about 3 years old and recently a problem has started where the picture comes on and then switches off after about a second and I am left with sound only. This happens every time i switch it on. I have tried leaving the tv unplugged for some time, as advised, and this temporarily solved the problem only for it to start again. Is this a problem I can fix easily and cheaply or am I better off paying for a new tv?