I have a motor that sometimes just shutters the prop back and forth and will not spin. This only seems to happen when starting the motor from a dead stop it does not happen in flight. Even if I try to go to full power the prop stills shutters, after a few tries it seems to finally spin up and work correctly. Any thoughts on what might be going on? I thought this could be a timing issue but have not tried to change that yet. Right now the timing is on low.