had similar on my '15, auto trans.
Same as you, only when I was really putting the spurs to her.
Turns out, I was bumping (I guess) the shifter out of position. It wouldnt slip into manual mode all the way - or vice versa..so it kinda "hung" between positions, this would cause nearly the same thing I think you are describing.
It would only last a second or 3, before it would slip itself into one position or another and resume normal accelleration.
Not sure if my shifter was defective or simply losser than others, if I wasnt fully dropping it into position (doubtfull) bumping it accidentally, or what...but once I figured it out, no more issues.
