Sounds like it got damp andthe motor brushes a stuck in thir holders take them out and give them a gentle rub with wet and dry paper on all surfaces after drying them gently by putting them on a radiator or similar warm place like an airing cupboard . Also put a roll of wet/dry paper into the brush holder holes so it presses onto the commutator while turning the motor This cleans the commutator If it does not work after replacing the brushes seek help from an appliance expert. Obviously if you can't get to the brushes to start with you need the expert from the start