The turntable on a microwave has the singular purpose of rotating the food while the oven is turned on. There are a number of situations that can cause the turntable to move erratically or stop spinning altogether -- none of which involves a defective motor or broken turntable. To get the turntable working again, correct the problems plaguing it. A few household supplies are all that is needed.
Baked-on food adhering to the turntable's bottom can cause it to stick to the guide assembly beneath it and wobble during the rotation cycle. Remove the turntable from the guide assembly. Turn the turntable over. Wipe the bottom edge clean with a water-moistened paper towel. Return the turntable to an upright position and place it on the guide assembly. Grip the edge of the turntable and rotate it a quarter turn clockwise to seat it properly on the guide assembly.
A misaligned guide assembly will keep the turntable from rotating evenly. Remove the turntable from inside the microwave and also remove the guide assembly that it sits on. Turn the guide assembly over. Spin each of the three wheels on the bottom of the guide assembly with your fingers. Turn the guide assembly right side up. Place the pole on the centre bottom of the guide assembly into the hole on the bottom of the microwave, if your microwave has one. Whether your microwave has a pole or the assembly sits on the oven's bottom, rotate the guide assembly a quarter turn clockwise. This will reseat the wheels inside the groove in the microwave's bottom. Place the turntable on the guide assembly and rotate it a quarter turn clockwise to reseat it to the assembly.
Dirt or other contaminants that have got onto the wheels at the bottom of the guide assembly can keep the turntable from rotating evenly. Remove the turntable and the guide assembly from inside the microwave. Wash both sides of the guide assembly with dishwashing liquid and tap water to remove any debris or other contaminants, paying special attention to the plastic wheels. Dry the guide assembly and wheels with a dry soft cloth. Return the guide assembly to the inside of the microwave. Rotate the guide assembly a quarter turn clockwise to reseat the wheels to the grooves on the inside of the microwave. Place the turntable on the guide assembly and rotate it a quarter turn clockwise to reseat it to the assembly.
Never turn on an empty microwave.