M.M.
My son did the same thing around that age where he would take about five 30 minute naps a day vs the longer naps he took when he was younger. I had read that a lot of that has to do with how much more active they are becoming and that are busy working on new skills. All I can say is that he grew out of it and now takes consistent hour or so naps twice a day. Sometimes I would try and rock him back to sleep if he was really fussy when waking, but it is hard to break that habit once it gets started.