Hope this makes sense...
A few weeks ago, I was wearing a top that kept slipping on one shoulder. I wore it a few times over a week and because it kept slipping down, I sort of lifted my arm up to get it back on.
I now seem to be doing the shoulder movement without realising. I saw myself on camera doing it the other day and now realise I seem to do it rather frequently. Tips are fine now so no 'need' to do it - seems to be a weird habit. 
HOW do I stop it?! All tips welcomed :)