As long as you don't see any signs of an RI (popping or wheezing when breathing, mucous in the mouth/nostrils) then he's just yawning for no reason, as balls are known to do sometimes. When they have an RI they sometimes "yawn" to try to breathe better, but if there are no signs he's just yawning. Nobody knows why they do it, maybe they just yawn to confuse us
On a side note, 97 is a bit hot for a warm side... If you have it on a thermostat I would maybe turn it down a bit, and if not I strongly suggest you get one