Why my car hesitates,then shifts hard on the first shit. Sometimes on the second on 2008 Pontiac G6

It will run good for days then start doing this had it checked out nothing can be found.When checked out a lot of codes came it but still is not fixed

Asked by for the 2008 Pontiac G6
are you getting any trans codes? what are your present codes?
I am having the same problem and the only codes that is coming back are saying tune up got a tune up doing the same thing
seek a diag from your mech