Servo motor swinging back to 0°
Try with something like:

#include &lt;Servo.h&gt; 

    Servo myservo;

    void setup() 
    { 
      myservo.attach(11);

    } 

    void loop() 
    { 
        delay(2000);
        myservo.write(50);
        while(1);
    }  


and let us know.
But more important: disconnect the servo +5V wire from Arduino and use another power supplier!!!