Drive plate motor stops working?

Panasonic Microwave oven NN-CT559W. Often when a container and food is placed on the rotating plate it works for awhile and then stops. I open the door and give the plate a shove and it will start again but then stops. The hand book says the max weight should be 4 kg. On weighing my food and container it is only 2.37 kg. With the oven off I can rotate the drive dog by hand in both directions without it jamming.
Assuming the motor needs replacing, is it a DIY job or a specialists job?