Easy fix.. Check your front tire pressure. Mine does this anytime one get 3 -4 lbs lower than the other. Just got back from a 2000 mile trip and it about drove me nuts one day, checked the pressure and one was low.
My friend who owns a trans shop and a few GM'* himself told me it has to do with the computer thinking the trans is slipping due to one wheel spinning more reves each mile vs th other. Sounds lke a line of bull, but every time mine does that I find a pressue diff on one of the fronts.
P.*. If you turn the key off for a minute and back on it will reset for a while then do it again if it is a tire.