It's probably just be the brushes on the motor. I have similar problem and was looking here for diagrams on how to get them out. If anyone knows perhaps they can let us know. Not sure if you can get them out (Hotpoint 1200 first edition) without removing the whole motor assembly.
If you switch off, open door and turn drum by hand just a bit then it may move the brushes a bit and it may then work for a while. The fact yours is intermittent means at least the whole motor is not kaput.
Ian Pedder, October 2006