My 2 yr old grandson wakes up and has trouble catching his breath.

He started doing this occasionally about three months ago according to his mom.  And is now waking up a couple of times a week this way.  She says sometimes she has to rub his back to help him catch his breath.  He is not crying or yelling.  He just gasps and then can't catch his breath.  She is taking him to the doctor this week to see if they can figure out what is happening.  She doesn't seem to think he is choking on his drool or acting like he is having bad dreams.  So I am wondering about sleep apnea.  He will be three in Sept, 2009, was not premature and has not had any health problems to date.