If you are feeling vibrations from the motor,when plugged in,there is a good chance that it just needs lubricating.
The lubrication may have dried up causing the motor to seize,it will still turn by hand but require too much force to get it spinning on its own.
Get yourself some service oil,3 in one or sewing machine oil,and apply a few drops to the motor's top and bottom bearing whilst turning the pulley by hand.Unplugged from the mains of course.Be gentle with the motor's spindle as a bent spindle is something best avoided.
You will have to be patient and keep repeating this operation,maybe for a couple of days, but it has a very good chance of getting the motor spinning again,in my experience at least.Gently warming the motor with a hairdryer may help speed things up.
Problem with the TD125 motor,and other Thorens',is that the motor cannot be opened unless you drill the rivets out so it's a matter of waiting for the oil to penetrate the bronze bearings or drill the rivets and replace with screws.
The motor is vibrating as it's trying to get going,good news!
Don't bother taking anything to bits before making sure that the motor is well lubricated and smooth.
Good luck and come back to let us know how you get on.