I think its because your tires are still cold.
Whats the outsite temp when it happend? You posted at around 10th month of they year so im guessing it was starting to get cold.
This ussaly happens to me on both my stangs more so in the shelby in the morning. As i pull out from my gates i ussaly hear the lovely sound of my tires swishing about for grip and the light goes on lol. eventually it stops and then the grip is instant.
On the shelby though you can tell the tires are warm when instead of swishing sound you start to hear squeeling tires when you get on it a bite more.
The V6 seems to just grip grip grip when the tires are warm unless the road sucks.
I dont want to complicate this but; the degree of throttle input, external temp, tire temp, and rate of tire cooling can determine how often this happens. Of course the relationship of all thouse factors with one anouther will show its frequency, ie. cooler external temp will increase the rate of the tire cooling.