how old is the bike and how long has the motor been acting up on and off, when was the last time you had a new battery?
possible the brushes are used up, because of old age.
there are places that rebuild starting motors, if only the brushes are fried then its possible to get it replaced.
My mechanic says always listen to the starting motor and make sure it disengage.
My guess is your battery is low and making it difficult for the motor to start the engine, old battery give off even lower voltage in cold mornings, and now your starter relay has been fried. fried starter relay can keep the motor engaged after you release the start button causing your motor to fail trying to keep up and getting dragged along with the crank.
if you can post a clear photo of the inside of the starting motor and see if its useable, if it is then you can bypass the starting relay with a test crank direct from battery.
Check your battery voltage as well and check if your starting relay clicks when you press the starting button.
Then we will know if you need a new motor, battery or a starting relay.
31210-KED9-900 0 MOTOR UNIT STARTER here is the part number.