2000 Dodge Durango Transmission Hesitation

I have a 2000 durango, I’ve had it since birth. (it’s, not mine), there was always a little hesitation between gears - even brand new. (auto tranny)

Anyway, when gas went over $4 pg., I stopped driving it and it sat for a while, now that I’ve fired it back up, the hesitation in switching gears is really bad.

It’s at it’s worst from 3rd to 4th I think.

In the olden daze - it was often vacuum related, so I did the obvious and drove it a good stretch to let things warm up.

So it absolutely does get much much better after it’s warmed up good, way less hesitation between gears.

So the question - is there any possible easy stuff to check here? Any chance it could be vacuum, or a particular sensor? It’s really been a great truck, other than a water-pump, I haven’t had to do anything with it. It just crossed the 100K mark.