Ive got a normal girl that does this exact same thing. Sometimes shell do it a few times when holding her sometimes I dont hear it for weeks from her. Shes as healthy as she can be. It can really make you go crazy though. The first few times she did it I swear I had her up to my hear for about 15 minutes trying to hear for any wheezing or popping sounds indicating an RI. As someone else said though, just keep a close eye