As Bimati mentioned check the POWER mode switch and make sure it's depressed (best overall mode & economy) as the WINTER or off modes shift funky. If you are in POWER mode, then check your ATF level. It's not the easiest thing to do since you have to slide under and remove a plug (17mm or 19mm) from a recess in the transmission pan. IIRC the procedure is in the owners manual, if not post and I or someone else will put up the section from the shop manual.