The problem will be a warm-up fault very probably in the power supply - the set is good when cold - then it starts to warm up and a component fails - turns off and gets cold - then turns on and gets warm.
Your choices are to take it to a TV doctor - get a new set - or try to fix it yourself.
If you try a home-fix a can of freezer spray might help - you squirt it on components you suspect might be the cause and observe what happens. The alternative is a hair dryer in an attempt to accelerate the fault condition.
Good Luck...
August 2016
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix televisions.