My 2001 V70 from time to time on the first drive of the day seems to stick in first gear when I pull out on to the road. The engine will rev up to about 4500 rpm and it won't shift until I let off the gas. 189,000 miles and don't know the last time it was serviced. I was thinking about draining the trans fluid and changing the filter unless someone has another suggestion.

 

Do a drain & fill and see how foul the fluid is.
There is no externally accessible filter.
AFTER you get the fluid clean consider using LubeGard (red bottle) in the proscribed dosage.