If you can easily get to the motor, they are fairly easy to take apart. Use only some oil and very light grease on the gears, the grease will get thick as it gets cold out. If it is only acting up when damp or wet out, check the connections for any corrosion. Better yet, remove the wires and cut off the end inch or so and make a new connection on both the motor and controller box connections. If the rotor is very old, the capacitor in the controller box may be drying out and causing the problem. It is a special non-polarized capacitor and is not easy to find.
***be carefull as there is lethal voltages inside the controller box. Do not attempt if you do not know what you are doing. Any tv antenna shop should be able to change this for you if needed.