Any one know whats causing this problem?

I have a whirlpool generation 2000+ built in oven. Was doing my Christmas Cake the other day which takes about 3 to 4 hours. I did a few buns first from mixture left over then put cake in. After about 2 and a half hours the cooker switched itself off and on the display it just said off. Anyyone know what this fault is as I am disabled and can't walk and I am scared this may cause a fire . Just can't understand the problem. Thought I had done something wrong but when I did cake again the same thing happened.