This is usually either from sitting over winter and things need to be freed up or the motor capacitor is failing. There is usually a cap on the end of the motor that can be popped off and has a slot for a screwdriver so that you can manually rotate the motor while the power is off. When the motor takes longer and longer to start and buzzes the capacitor needs replacing. If the pump is new, make sure that the correct voltage is being applied to the motor. Either 120v or 240v and the wiring diagram will be on the motor.