Could be the heater element, could be a bad connection, could be an intermittent fault on the circuit board. You could keep on guessing and maybe one day strike it lucky and find the fault. You don't say if you own a test meter and have some basic fault finding knowledge. Without them you would be better off giving it over to someone who can test it and find the fault quicker.
Linoln Appliance NZ, June 2013