I'm not an expert and I don't know that much about electric motors either but I did major in that type of thing in high school many decades ago. A lot has changed since then I'm sure but if my memory serves me correctly (and it doesn't do that so much anymore) I'm feeling a capacitor issue here. If the motor does not have a capacitor then we have already exhausted my knowledge of the subject.
My recall is that capacitors are used to start a heavily loaded motor and get it to a certain rpm at which time the capacitor leaves the circuit and the motor runs on its own with less need for the added assistance. It takes more juice to start an electric motor than it does to run one. Once the initial start-up load/drag has been overcome the capacitor is no longer required.
Doesn't sound to me like the motor is able to reach the "run" stage.
Hopefully someone here will come along with more knowledge than I have about such things.
In high school I built an electric motor from the ground up. I personally hand wound the windings and all that stuff and the damned thing actually worked. To this day I remain impressed with my ability in that field. But, that's as far as it goes. You now know what I know.