Hi I am Vortash
There may be actually nothing wrong with your set ? .......
This set has an anti surge protection circuit and it is designed to shut down should the incoming power peak above 240 volts or more , is this happenig at random times or around the same time in the evening or day it may be that this safety device is protecting the set .. sometimes local area transformers peak at the time of most consumer requirements this may just coincide to when you sit down to watch tv .. however if it has a habit of doing it at different times during the day .. then this safety circuit may be at fault and require an engineer to service the tv and check for poor components that have changed value .. It explains this is in the manual if you do not have one for your set you can download one for free from http://www.safemanuals.com
hope this is of help regards Vortash