Why do the P4 motors do a couple of quick rev's upon starting? Since the props don't appear to be self tightening as were the P3, this seems to be an unneccessary stress on the motors and props....

It is part of the motor system initialisation, it is necessary, don't worry about it.

Hi, it's normal, please don't worry about it.

This is the first phantom (4) I own, are the motors supposed to sputter like on take off in the first few feet on it's way up (interrupted) thrust. I also own an s550 w/Naza and DJI tuned propulsion system and it does act the same. Scary almost seems like the P4 is going to fall out of flight for the first few minutes of flight.