My 26 inch Vizio flat screen comes on by itself in the middle of the night, about once every week or so. The timer is not on. Otherwise it works fine. Could it be external remote control signals from the neighborhood. No other houses within 50 feet.

It's highly unlikely that it's a signal from the area. It could be that something in your house uses the same signals though. I have seen TV remotes turn clients' fireplaces on before haha.

To test this, you could cover the sensor on the front of the TV with tape or something so that the remote does not work anymore. If it still comes on, then that eliminates external forces (unless of course someone is pressing the on button manually).