As long as you can isolate and confirm that it is in the TV (and not a quirky streaming device or receiver) flipping on and off, I would point to the power supply first. I don't work on the internals of our gear professionally, but I have brought back many a TV from the grave with an easy power supply swap. Shop Jimmy is a good spot and there are a few others too...
"There's a big difference between winging it and seeing what happens. Now let's see what happens." ~MacGruber