Give these troubleshooting steps a shot
Unplug the TV for 30 seconds.
Unplug the TV from the wall outlet or surge protector for 30 seconds, and then plug it back in.
Try to update the software.
In some cases, a software update can correct the problem. There is a risk, however. If the TV turns off during the software update, it could damage the TV. Updates can take up to 30 minutes depending on network speed, so if the TV is not turning off too frequently, try updating the software.
Disable the Power On with Mobile option.
TVs which can connect to SmartThings can be turned on using compatible devices, sometimes automatically. However, if abnormal "power on" signals are sent through the wireless network, they will trigger this function and make the TV turn on.
If you do not want this function, navigate to Settings > General > Network > Expert Settings > Power On with Mobile, and turn the setting off.
If the TV continues to turn off and on by itself continuously, visit the Support Center to request service.