I just had my girls into the vet yesterday and they got a clean bill of health but my lilith sometimes does the same thing. it is usually while she is sleeping though. The vet said her heart and lungs sounded great so I shouldn't worry about it. I thought maybe she had a touch of asthma (SP?) But vet seems to think not. I wondered also if maybe she is dreaming and whatever she is dreaming about makes her do this. I really don't know. But mayeb your vet is the best bet. I know it turned out to be nothing with Lilith according to the vet. But better safe than sorry.