Televison turns off after about the first hour,than more often after that.
Your telivision may have some loose solderings insde we thinks. According your report, your TV works for an hour or so and turns of automaically, and turns off more often after that. Ok.
In every telivisions, there are some parts gets heated while working, and is normal too. But after a prolonged use, the soldering points of that component, usually resistors, will get heated too. When it his heated and cooled for several times, loose soldering will evolve, and it cannot be detected by normal methods.
The only thing we can do is to resolder all solerings of the suspected section, or that critical point.