Won't shut off. I have a GE microwave model wes1450dm1bb. Today when I opened the door, put

Question

I have a GE microwave model wes1450dm1bb. Today when I opened the door, put something in and then closed the door the microwave turned on and wouldn't shut off with the stop button. The only way to get it to shut off is to open the door, but as soon as I close the door it starts again. I have unplugged it a number of times but the problem remains. Any idea what is causing this?