RPM Inconsistencies

2012 Range Rover 5.0 S/C

An odd issue that I've noticed and I'm wondering if anybody has experience here or if this sounds familiar:
RPM on the highway will fluctuate every 3-4 seconds, up about 200rpm then back down, then up, then down, etc. Every 3-4 seconds at highway speed. There is a very slight shake in the car when it fluctuates back down to the lower RPM. Once I step on the gas hard the issue goes away, and if my foot is completely off the gas it goes away. Any ideas?

Thanks in advance