My TV just did the same thing after I swiveled the TV the the left. It immediately started turning on and immediately off. I unhooked the HDMI cables and then plug one back in as it was turning off and on. When I wiggled the HDMI connection the TV came back on and now works fine. My guess is the three HDMI cables pulled on the board in the back and cause a connection issue. My way of fixing it could cause a short so use your best judgements.