HELP!!!Breathing problem or what??

[Chikie]

Hi im new to this forum and became a member to something my chicken has. I just recently noticed that when she sits down, she rocks back and forth as if she is having difficulty breathing. She like takes deep breaths. She eats well and drinks plenty of water its just the rocking back and forth part that has me scratching my head. And is it some disease and if it is please tell me what vaccines to use. Thank you in advanced