Onn Roku TV keeps flashing on and off

I have an Onn Roku TV that is 5 years old. Today it is now flashing on and off. The only way to stop it, is to unplugged it from the outlet. When I try to turn it on it continues to do this. I have turned it on with the remote and with the power button and it still does it. I can’t even get to the settings to do a reset because it instantly starts flashing.