my Hitachi 28in widescreen 3 years old, keeps turning off?

Most notably this occurs when first switched on in the morning but it can happen at any time. The picture will suddenly disappear as if it has been switched off. Sometimes if will turn back on by itself, other times I use the remote. Sounds like some sort of loose connection or even one of the scart sockets. I've had the back off but cannot see anything obviously loose.