My TV has started getting lines across the screen and making a high pitched noise, whats wrong with it?

Question

My TV has started getting lines across the screen and making a high pitched noise, whats wrong with it?
This stops happening after the TV has been on for a while, but is really annoying. Ive checked and rechecked the connections and all are fine.

Answer

dry joints or l.o.t. playing up not a diy job