You give me no clue as to the model, manufacturer, type or age of your machine !!
So I'll make an educated guess: i) the fill solenoid is intermittantly open circuit. ii) there is a blockage in the base of the pressure chamber and it prematurely but temporarily actuates the fill pressure switch. iii) somebody is winding you up by turning off the water or electricity intermittantly.
Repairman
April 2009