Hi, Wanted to post this because some of the existing answers are inadequate and some of those threads are locked to further comments. I have a Samsung UN55KS9000FXZA led 4k Bought in March 2017. My symptom was fairly dramatic, every evening when I turned the TV on to Comcast it would blink on and off, making it unwatchable. Power cycling the Comcast box fixed it for the next few hours that you would watch TV. It wasn't the TV, if I switched to streaming Amazon or Netflix the picture was fine. Some threads say say setting the Picture Mode on the Samsung to Dynamic fixes this and my picture mode is set to Dynamic. I did find something that helped which is why I wanted to post this. The new Samsung's have a small box cabled to the TV that connects up to 4 hdmi inputs, one of which is Comcast obviously. When I seated and unseated the cable to the Samsung TV from this small, 4 hdmi input box with the television turned on it got a lot better. It wasn't perfect, it occasionally blinked on and off but it was a lot better.
Dead thread from last year now being closed.