I have experienced this on my 2019, and it’s always from a stop; I also feel a slight slippage, as if I have a cardboard box, sliding back to the tailgate, very slight, but noticeable!
I only have 4500 miles on it and it has done it since day one!
I took it to the dealer and they found nothing on test drive, and no supportive codes. I traded in my 2010, and know how the vehicle should respond!
Now this is a guess, on my own, but moving from occasional stopped position, it could be a delay in the Brake Assist Feature. I also mentioned this again to the dealer, but they said they didn’t think so!
So that’s it so far! I will check the transmission fluid and continue to post further occurrences!
Thank You,
Vinny 😊