v_centerspeed
This variable sets how quickly your view returns to the center after looking up or down and moving after that and "lookspring" is set to "1". This variable is only useful to people who only play with the keyboard, have "lookspring" set to "1" and do not have "+klook" or "+mlook" enabled at that time. When the player moves the distance specified in this variable the screen will pop back to the center position.