Chest shimmies are one of the easiest moves yet one of the hardest for many to master. I think there is a lot of social stigma to it that could create a mental block, maybe I am wrong ... But there is definitely something to be said for the fact that it is strange to have difficulty with a move that is so simple. right? 

Well let's forget the stigma and focus on the technical part then. what are the most common mistakes beginners make when they try to learn the chest shimmy?