Billiards is about consistency, so why would you want to complicate your mechanics by moving your body? There is absolutely no good reason to move your body during a shot except possibly on a power break.
Always keep your entire body extremely still during your final stroke. The only muscle you need to contract is the bicep of your shooting arm. Your wrist and grip should be loose to not twist or steer the cue stick.
Pay attention to your body the next time you practice and notice any extra movements. Try to eliminate them as part of your routine and you will see your pocketing percentage skyrocket!