Gym friends?

It is a simple fact about me that I am not outgoing.  I am incredibly shy.  Once you get to know me and I like you, I will not shut up, but until then, I do not have a lot to say.  Consequently, it has always been a challenge for me to make friends in situations where it is not absolutely necessary to my survival (ie, school).  So, the gym is troubling to me.  In the locker room, I hear other women chatting away about their families and their hair stylists and their spin class, while I duck in and out of my locker and about my business.
Obviously these people met each other somehow, I just have no idea how to do it.  I go to classes, but talking before yoga never feels quite appropriate, and in most other classes, I'm too out of breath to even think about trying to make friends, let alone actually speak to anyone.  And now I've been going to my gym for almost six months and so I feel like I've passed the threshold for "hi, I'm new, tell me about [insert conversation topic here]" intros.  Suggestions?