oric_dan:
As noted, some servos, such as GWS, twitch much more than others on power application.
Other than finding servos that don't twitch, it may work to use a Mosfet to apply power to the
servo [p-chan Mosfet on high-side power], and start the incoming pulses before power is applied.
Maybe.
This works with the servos I have. After I power on the Arduino, I manually connect the servo to power and there's no twitch. So I know the P-chan Mosfet circuit you describe will work.
I swapped my Uno boards and the twitch is still present. When swapping servos on the new Uno, one thing that was interesting is that different brand servos twitch in different directions (ccw vs cw). I'm ordering some other servos today. If that doesn't do it, I'll do the Mosfet design.