Why Does My Toilet Start Running All by Itself?
Your toilet is in need of a repair. Water is slowly seeping past the rubber flapper in the bottom of the toilet tank. This piece is supposed to be closed except when flushing. When this happens, the water level in the tank slowly drops until it reaches the same point in the tank as when you flush it, and the water comes on and starts to refill the tank. Replacing the flapper will take care of this problem.