how do i fix my moffet cooker?

whilst cooking tea tonight my moffet mss 601 cooker switched itself off.. (asif the electric had tripped out) so i checked and nothing had tripped. i switched the dials to off and turned it back on it came on for about 20 seconds and then went off again. the timer is still working as you can hear it counting down but the oven itself will not come back on... PLEASE can anyone help??