I think your TV shuts off due to a defective board. The problem could also be brought by the power supply or the control circuits are destroyed. You need to reset your TV by removing the power cord and then plugging it back.
Alternatively,call customer service in your TV book that came with the TV. They will find you a repair shop near you to get the part you need to replace. If it is not replaced it will eventually burn out and the TV will not work at all. I hope this helps, I had similar trouble with mine, had to replace the part.
I would recommend you these techs (www.tvrepairjacksonvillefl.com)
andrew
July 2012