I have a 2003 Impala LS with the 3.8 V6. The transmission started slipping.

WOOOW! SCARY! Mine does the EXACT same thing! I work 35 miles away from home & It does it about 2 days out of the 5 day workweek (getting to be more frequent, though!). It seems to ONLY do it on my way home after work (sitting in the hot sun & it's a black car), never on the way (after sitting all night in the cold)...(maybe temp. related???) when I 1st start it after work, I pull out of the parking lot & go about 2 blocs to a red light. When it turns green, I go to go but the car don't move....I give it gas & the engine just revs up & then WHAM!! it "catches" & I finally go after about 3-5 seconds! It may or may not do it 1 or 2 more times, then, it seems to "stay engaged" after that. Another thing, is when it does this, all the way home, every time the car shifts up or down, instead of smoothly shifting from 1 gear to the other (which is almost un-noticible), it "slams" from 1 gear to the other. (like u dropped the clutch after shifting gears with a manual transmission instead of letting the clutch out slowly.)...I've been getting worried as it seems to be becoming more frequent...ANYONE found a CURE? I bought my car used, but bought the LONGEST, most complete warranty they had, so...I wanna know if this's something I should take in asap, or not.