Jan could be right with the impeller being crudded up and over the winter the junk in it could have caused it to put enough of a load the motor couldn't start. If that was the case then there is probably a lot of friction in the impeller area. Normally the impeller doesn't touch the pump body but there is very little clearance. Now with it running you may be generating enough frictional heat to cause the seal to go or something to warp. Or, could be the motor bearings seized. You can get to the impeller through the pump basket chamber. Reach in the hole and see if you feel any crud. As Jan said, be sure the thing cannot start or you'll lose your fingers. Kill the circuit breaker. You can use a wire hook (coat hanger wire) to help pull stuff out if you feel something.
Al