I have this same TV model but I have no problems. Since the symptoms happen after a warm up, I suspect the power supply, because I have seen similar symptoms on a different TV brand.. One of the voltages has dropped, causing this massive failure in display, signals, and audio. The power off period allows the supply to cool off, but returns after the warm up.
If you don't have the resources to check and replace the power supply, go to a professional technician.