My TV is switching itself on and off after a while.

What type of TV, and how old? Do you mean it's going off, and then back on, or just off?
Try vacuuming the vents, especially on an older bulky CRT TV.
Answer back if that helps.
Is there anything new plugged in on any other circuit the TV is on?

Please provide make and model.

If a newer HDTV, make sure HDMI-CEC is disabled.

As already asked, is the TV randomly turning itself on? For example, will it suddenly turn on in the middle of the night if it is not unplugged? Or does it cycle on and off when you try to turn it on?