Rapid pulsating

So my baby boy keeps doing something very strange I'm almost 35 weeks he is head down its a rhythmic pulsating where his back is and then when he is done doing that he gets the hiccups I have research it and I guess it's practice breathing I used my Doppler when he was doing it and it appeared to sound like that's what it was is anyoone else experiencing this its so weird 😱😱😱😱