Could be tires out of balance (among other things like worn stabilizer, alignment, etc.). My advice is to have dealer rebalance front tires and then agree to pay for front end alignment once you've got the coach loaded "wet".
Keep in mind that motorhomes do not drive like cars or pickup trucks. They are big boxes on big truck chassies. You'll sense vibrations, noises, swaying, etcetera in a coach. To help with your perception of the problem, you might try riding in a friend's MH, or maybe taking a friend with you when drive this Adventurer again...