Ensure all your taps are turned off fully.
Make sure that the water is not running down the back of the toilet pan. If you have water running down the back of the toilet pan, it would indicate that you have a problem with the inlet valve / ball valve or push button syphon in the system. This will cause your pump to hunt (turn on & off randomly).
Ensure the thermostat on the immersion or central heating stat is set at around 60 degrees. If it is over 60 degrees the pump will possibly leak on the shaft.