Runs for a few minutes then stops

ok, the machine will run in a working situation for 2 minutes then motor keeps running but vibration stops. The arm that causes the vibrations can be rotated about a half turn and the machine works again for 2 minutes, then stops vibrating again. I'm not going in until I have a plan. I'm thinking the serpentine belt is shot or the pulley it wraps around has worn smooth. Is this common?

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The motor continues to run, but sanding stops. they turn the "connecting rod" that runs sander, kick the !&&* out of it, and it runs for a few more minutes then stops. Motor doesn't seem to be overheating

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