Color wheels are the first place to look, but I can't see this being that, unless someone else has seen the same thing. Can wee assume it is all inputs including the internal tuner and viewing the menu?
It's obviously a 'thermal' issue. As the bad part(s) warms up, it stabilizes. The trick to find it is using a 'freeze' spray, isolating small sections of the video process section(s) of any board(s) involved.
Abundant OTA television is what makes this country different from all others. Lets keep it this way. If you like Wi-Fi so much, OTA fits right in. After all, it is wireless.