What you're talking about is when a cat is "kneading" their paws. They did that when they were nursing kittens to get their mother's milk stimulated. It is said that they will carry on this trait when they are adults and when they "knead" it gives them a since of comfort. They "knead" when they are content and happy, just like they were when they were with their mum. So, be happy! Your baby thinks of you as his/her mom!