Mine was working as it should and now the motor is stuck. It's still getting power and just buzzes but isn't vibrating any longer? Easy fix or trash it?
Generally when you see what you described the motor has an open winding. Not repairable - replace the motor or the entire vibrator. Most of these units are coming from China so you can't expect them to hold up long. I think I trashed two and then bought one from Midway and it has never failed in years of use. They are just like the cheap fans you buy at Walmart except the vibration causes them to fail even faster. About all you can do is buy a name brand that has a good warranty. Call them up and ask them if they will supply you with a new motor.
you can check, i have had the motor become disconnected from the weight that is spins under it to make the vibrations. Sometimes is a replace a pin etc toi reconnect some times its a chunk of cast thats gone, at that point maybe but for the price of a new one probably not worth it. What brand is it?