TV has mind of it's own..

My TV is only 4 years old but keeps turning itself off/standby for the first 20 minutes of turning it on. Once up and running it stays on (a bit like an old car starting on a cold morning). The picture is good but sometimes you get a black margin at the top of the screen which is easily resolved by turning it off/off.

Can anyone advise what the problem is likely to be and how much it would cost to fix (or is it on it's way out?)

Can't help you personally but I'd suggest posting the make and model.Someone on here's usually got an answer but they need something to work on!Hope that helps you help someone help you(does that make any sense?!?!).

It's a Hitachi 28" Dolby Pro Logic widescreen TV, approx 4 yrs old. Not sure on the model number.....