If the power is actually turning off then back on, check to make sure that it's the power socket, securely. If that's fine, it's a fault with the TV. If the TV's staying on, but the output is turning off then back on, it's a problem with communication via the antenna.
The problem could be that the sleep time is on and set for 1 or 2 seconds. It could also be that the power cable is not connected well. You need to check that the power is well connected and the settings are turned off.