I have a 2001 Chevrolet Lumina Sedan, not LTZ, or LS, and when i first purchased it, it had 39,000 miles on it, and it was going that same thing for me. The tranny would kinda jump, or jerk before it locked into 2nd, mainly under hard acceleration, and sometimes normal. I just rode it out. I said, damnit if the tranny is going in this new car, I cant believe it, and wouldnt you know it, a month later, it shifts as smoothly as any new car should. As for the LOW TRAC light, thats just normal to come on too. Its just your ECM going through its startup diagnostics. Good luck with it. I would however have the tranny fluid flushed. Or maybe just check it. Drive your car normally for about a hour, and stop, leave it running in park, and pull the tranny dipstick, and check it much like you check your oil. If its red, your in the clear. If its black, and has a funky smell to it, say goodbye to your beloved car, and sell it before a new tranny is needed. And FYI, average milage between tranny flushes is about 40,000 miles.