Use an animation.
Or use gradual motion using the MAthf.lerp function to make it slowly sway from side to side.
But an animation is MUCH easier.
answered Jun 12 '11 at 04:36 AM
make it rotate the same way you make the camera rotate. it is simple. one problem you may find is that it begins to move off of the screen. this is simple to fix just use the Mathf.Clamp() function that is how i did it