whats wrong with my diplomat softline 700Ga gas cooker?

i have a 4 yr old diplomat softline 700Ga gas oven that we brought from MFI and there seems to be something wrong with it,everytime i turn the cooker on the ignitor keeps clicking like it should only do when oven is first turned on,the oven could be on for a few hours and the ignitor clicks on every so often this should not happen,could you tell me what the problem could be!! thank-you