Have sound but no picture

I have sound but no picture. This happen all of a sudden turned on tv no picture, had no lighting, no storms, no power surge. However a couple of times in the last 2 wks when I turned on the tv, the picture was distorted looked like you were looking through a bottle, picture was rounded and the colors were off. Turned tv off & on and it cleared up. I did try to unplug the set, let it sit for 2 days same problem.