The automatic transmission on my 2000 Subaru Legacy wagon up-shifts very hard when cold. I’m not sure if it’s first to second or second to third. I’ve just had the fluid replaced, but it didn’t help.
Do any of the additives do any good?
Holy water might.
It sounds like you need to take it to a tranny shop for an evaluation.
That could be computer related or mechanical. I would let a trans shop check it to be sure. It could be something as simple as a sensor…
transman