Servomotor misbehaves

How can i eliminate servomotor jitters? Also when i turn the power on, the servo rotates.

You need to describe the problem in a lot more detail and also post the program you are using.

When you attach a servo the default position is 90 deg so if the servo was not at that position it will move immediately to that position. You can do Servo.write() before you attach().

It takes a little time for the Arduino to boot and get to the Servo.attach() code and in that period the servo may be powered up but without a suitable signal. Some servos can move erratically in that period. For some servos that can be stopped by fixing a 5600 ohm resistor between the servo signal wire and GND.