We have a 2006 Nissan Pathfinder LE V6 4x4. While driving for first 20 minutes or so there is a jerking around 50 - 60mph only during acceleration. If you let off gas it stops, if you speed up it stops & after driving for some time it goes away. There are no warning lights & no codes. The vehicle idles perfectly, runs & drives perfectly with exception to this jerking issue. Any assistance would be greatly appreciated.