If the bowler asks you to move back (or forward) a little because of the style of his run-up, do so willingly without complaint. Stand absolutely still when the bowler is running in and delivering the ball so as not to distract the facing batter. If you are in the way of a bowler or fielder trying to stop the ball or take a catch, they have the right of way, so move out of their way.
It is the same for the square-leg umpire. You must be quick to move if the ball is heading your way and a fielder is trying to get to the ball. In doing so, however, make sure you keep your eyes on the crease line as you may be called upon to judge short runs by the batter or a run-out appeal.
Umpiring at square-leg, although needing less intense concentration than at the bowler’s end, is not an excuse to totally relax. Much ill-feeling is caused in junior or lower grade cricket when a player umpire is not watching the play when an appeal is made for a stumping or a run-out.