Hello, my name is XXXXX XXXXX I will help you with your microwave. The turntable is driven by a small electric motor under the floor of the oven. The motor may have failed but some models have a setting to turn off the turntable for when you put in something too large to turn. Have you checked to see if the turntable is turned off? I will look up your model to see if it can be turned off.
Yes, that is normal for the turntable to try to reverse if it gets stalled. I can't find the exact owners manual but the two closest ones do not show a feature for turning off the turntable. The motor has two wires going to it and is 120 volts ac motor. It would need to be tested to be 100% sure but I think the motor has failed. If you have a meter you can test for voltage and if present during operation it will need to be replaced. The Panasonic part number is(NNN) NNN-NNNN