Microwave turns, gives out strong burnt plastic...

Question

My microwave made some flashing and buzzing when I heated frozen sausage (only for 10 seconds then I stopped it), and then gave out strong burnt plastic smell. Now if I put a glass of water in it, it will turn and light up, but in a few seconds there will be strong plastic smell, and no heating as far as I can tell for that amount of time.What might be the problem with it? Is it self repairable? (Sharp R-161X overrange model) Thanks for the advice