Will analog servo work with Arduino servo library?
Jitter can be caused by a lack of power, in which case it will be an irregular pattern that leaves the servo in the wrong place or it can be caused by the increment commands not being sent to the servo smoothly enough.

Have you got enough power for the servo? Where is the power coming from, does this output match the datasheet?

This analog servo requires PWM, so is pin 3 of you board PWM capable?

How fast does you servo rotate?  At the moment you are saying 1degree every 15ms, I suspect that is too slow and that's why the arm is coming to a stop and then rotating again which is making it jitter.