Create a text file called autoexec.cfg in your Doom3 'Base' directory and paste the following config commands.

seta pm_runbob "0"
seta pm_runpitch "0"
seta pm_runroll "0"
seta pm_bobpitch "0"
seta pm_bobroll "0"
seta pm_bobup "0"
seta pm_crouchbob "0"
seta pm_walkbob "0"

If that still does not help you could try playing singleplayer in third person with HUD and crosshairs enabled

seta pm_thirdPersonDeath "1"