I used to have a saw that would occasionally refuse to start. It was
sawdust geeting into the motor and clogging the centrifugal switch that
powered the starter windings. You could hear the motor hum but it just
wouldn't start moving. Sometmes I would just take a stick and try to
get the blade spinning and the motor would take off. It took a couple
hours to disassemble the motor to clean the inside.

I doubt that this is the problem described here.

Dick