It may be a safety thermistor component inside tripping as it overheats just as you suspect - working like an electrical fuse, but responds to heat instead. They can go faulty and start turning the power off too soon
Another possible cause is a dry solder joint (very common problem). It's ok while cool, but after a few minutes of being on, the heat in TV causes the tiny solder break to widen just enough to switch it off.
If you can leave it on with the fan blowing on it, and it does keep going on & off without you touching it, then i'd say it's 95% certainly a thermistor.
If it turns off, and you have to turn it back on manually (it goes onto standby or off completely), then it could be either, causing the problem.
Another final thing I see as possible is, the screens inverter can be heating up and going off (the TV will stay on really, but the screen will go black as if it's off, and when cooled even slightly it can turn back on again. You can check this easily by putting a bright lamp close up to the screen. The picture will still be there, but very very dark - a flat light gently touching against the screen will allow you to just about see the TV picture.
(the screen inverter is a special high powered circuit that takes a lower voltage (usually about 12 volts) and converts into a huge amount needed to work the powerful bulbs in TV screens.
Answers & Comments
It may be a safety thermistor component inside tripping as it overheats just as you suspect - working like an electrical fuse, but responds to heat instead. They can go faulty and start turning the power off too soon
Another possible cause is a dry solder joint (very common problem). It's ok while cool, but after a few minutes of being on, the heat in TV causes the tiny solder break to widen just enough to switch it off.
If you can leave it on with the fan blowing on it, and it does keep going on & off without you touching it, then i'd say it's 95% certainly a thermistor.
If it turns off, and you have to turn it back on manually (it goes onto standby or off completely), then it could be either, causing the problem.
Another final thing I see as possible is, the screens inverter can be heating up and going off (the TV will stay on really, but the screen will go black as if it's off, and when cooled even slightly it can turn back on again. You can check this easily by putting a bright lamp close up to the screen. The picture will still be there, but very very dark - a flat light gently touching against the screen will allow you to just about see the TV picture.
(the screen inverter is a special high powered circuit that takes a lower voltage (usually about 12 volts) and converts into a huge amount needed to work the powerful bulbs in TV screens.