Universal remotes, the most common cause of automatic relays, is caused by most universal remotes when they are within a 50 foot radius of the television set's receiver. This happens unpredictably but most believe the cause to be coordinated signals transmitted from a remote. These happen usually every 20 seconds when the remote searches for a homing signal, this homing signal is transmitted when most television sets turn off and on. Universal remotes receive the signal and transmit their own in response, hence, causing television sets to turn back on or off. Many owners of new, unprogrammed, universal remotes find themselves scratching heads when their television set turns back on and off unexpectedly.
Microwaves also cause these strange "relays" when they are just plugged into an outlet for the first time. No one knows for sure why this occurs but speculation is that small chips inside the microwave transmit high powered sound pitches that a television mistakes for a remote frequency. This usually only turns a television on.