Don't try powering the Arduino and servos from the same power source. Nearly all the problems
people have with servos are power related. Most servos need 1A or so peak, more than USB can
provide, much more than small 9V batteries can possibly supply, and servoe put spikes and noise
onto the supply that can damage or reset logic chips.
Motors/servos on one supply rail, logic on another (regulated and spike/dropout free) supply. Common
the grounds at the Arduino. Thats the key to trouble free behaviour.