My Sony Trinitron KV-19TR20 picture keeps blowing out?

When I turn on my TV, the picture is great until at maximum is it on for 15 minutes and I lose picture and sound and only get gray fuzz on all channels. When I turn the TV off for about 10 minutes, it works until the whole process is repeated again only in less time, I only get a good picture for about 5-10 minutes. Is this something I can fix at home with parts or is it worth taking to a repair shop? I am a woman, please explain simply...Thanks.

Super Susan
January 2005