You seem to lose precious fractions transitioning from the serve finish to actually moving in.
I would be expecting to see you hand with more forward momentum and then explode into the court with the initial steps. As it stands there seems to be a pause after you send the serve down.
edit....having another look it looks like the issue is more pronounced serving on the deuce side - frequently you seem to land with your feet behind the baseline.
I'd imagine someone with a decent topspin return would make this very uncomfortable for you.
I only skimmed the thread so apologies if the reason for this has already been covered. Good luck.