Why does my Sony Trinitron KV27TS27's picture turn to snow?

While I am watching a movie or playing a video game, my Sony Trinitron KV27TS27's picture will suddenly turn to snow. Sometimes it will turn back to the picture within a few minutes while other times (like now) it will stay snowy. Sometimes, instead of turning to snow, the picture will start to wiggle and tease me as if it's going to go off again. My umption is that it's just old and worn out, but perhaps it could be something else.