If using convection mode then preheat for 10 minutes. If you are making a microwave cake then preheating is not required.
Need your suggetions Not able cook gud cake. Dont know what happens with cake batter..may not mixing properly.
I suggest go by the microwave book as for their instuctions regarding baking As cakes cum out better in Conventiinal Ovens or OTG S.
Initially it's good idea to go by the book, Later when u get hang of it , you can modify Love