Squeaking

Is it normal for a baby to squeak when she sleeps? I'm not saying she occasionally squeaks - I am saying it is at least every 15 minutes there are at least 2 major squeaks followed by a grunt. It is almost like she is in pain but I know she isn't - she is normally just stretching. She only seems to do this when she is in her crib or pack n play. It is just very strange to me!