New engine behavior rhythmic ocsillation while accelerating

It begins to occur approaching around 3,000 rpms in the lower gears, and I usually drive in the high 50's (56-59) sometimes a little faster, but at 59 mph I'm at about 2,000 rpm's and everything is normal. It only occurs at lower gears at the top end of the range of each gear, and letting off the gas will cause the shift into a higher gear with the "oscillating" stopping.