Acceleration problem

My 2016 Altima is experiencing a sporadic
delay when accelerating from a stop.  It won’t
rev or do anything for a couple of seconds no
matter how far down the pedal is.  Then all of
a sudden it’ll go.  There is no check engine
light and no codes.  If I turn the car off, it’s
like it resets and has more power afterwards.    
The dealer has consulted their “tech line”,
could not get it to recreate, and has no clue.  
The sensor associated with the brake pedal
was changed by them and now it just did it
again.  The dealer is at a loss as to what to
do next.  Any thoughts?  I see a lot of talk
about the throttle position sensor, but the
dealer says it’s not it since there’s no code
being thrown.