Thanks for the info.
It is LG 50 inch plasma TV
and there are few circuit boards inside TV that can cause such symptoms, either power supply board isn't providing sufficient volts to other boards in TV or sustain boards located on either sides of TV has failed thus TV goes to protection mode and shuts down.
It needs further troubleshooting with multimeter inside TV to check output volts of power supply board to see if it is working properly?
If power board found OK then any of sustain board would be short and swapping it will help to resolve the problem. Please reply back if you wish to repair it yourself and have multimeter and can check volts on circuit boards in TV to assist you further and check following board supplier to get required replacement board or search/google it with the part number off of board to get better price and stock info..
If you are not comfortable working on it yourself then you may please use following link to get list of TV repair shops in area which will help to get repair quote...
I'm sorry there is no easy or quick fix for this problem and it is definitely hardware failure that needs defective board replacement to resolve the issue. I trust my input will help you out to make decision about this TV repair or invest that money on new replacement TV. Please feel free to respond if you have any additional questions.
A positive rating to answer would be greatly appreciated, please click on smiley face/star on this page then click submit/finish button so I can get credit on website for my work.