Oscarpeppa

Hi,just wondered if anyone had an answer have a T reg Galaxy automatic with a newish gear box not quite 3 yrs old.had a problem few weeks ago goes into 1st and 2 nd gear fine but does a bit of a jolt going into 3rd the last few days it's been taking longer going into 3rd although once engines warm it's ok.Going to be looked at on Thursday but was just hoping for a few positive feedbacks as dread the worse!!