How to remove pause (or jerkiness) when swimming free style?

Hi, When I am swimming freestyle, my left arm seems to pause briefly before entering he water (the right arm works ok because that's my breathing side). I am not sure how exactly I developped this problem because I didn't swim like this when I was younger. It could be that I did too many catch up or delay entry drills several years ago... However, I don't quite feel the pause during swimming and that's why I can't quite correct it. Any tips or drills that I can use to "cure" this? Thanks in advance! -asgard