My 380 does the same thing...
it will take a moment from P or D and then shift hard into reverse. If it is not from low fluid levels (which I am about to check), is it from the much higher gear ratio in reverse, or is it a sign of a larger problem? My transmission also has this annoying habit of taking a second (usually less) between 2nd and 3rd on a cold start (less than 10 min warmup time, less time, longer wait to gear). If I run it around town, it stops, and as long as I do a warm start (w/in a few hours) it doesnt do it.
Oops, sorry. Didnt mean to try to hijack your post...
Thanks for any advice anyone can offer to us with trannie probs!