i had the same problem and after i unpluged all cables ( i wanted to see if an external device is making any trouble) and put them back in, the problem stopped. it must have been a loose connection.
I have a Samsung TV connected to a Roku box and from about a month ago it has started turning on and off. I thought it was the capacitor problem that people were talking about and called Samsung. They sent a technician who said that all my capacitors were fine. he replaced it anyway but still my TV keeps giving me the same problem. It will work for sometime and then randomly switch on and off. Sometimes it will make a jarring sound and then turn off. The Samsung technician said that it has to be a motherboard problem and will cost $300 to fix it. What are my best options? Should I pay $300 or should I try to find the motherboard and fix it myself?