Why do my servos jump to one side when i turn on the power supply?
What is probably happening in when you power on, the Arduino takes time to reset and initialize the IO pin to the servo. As such the servo thinks it is getting a command. This is bad and can actually damage a cheaper servo.

You probably need a pull-down resistor on the servo line to keep it from getting a signal till the Arduino has a chance to initialize the IO pin. 







simulate this circuit &ndash; Schematic created using CircuitLab