Under the rules there is only 2 possible "states" for a back who was initially set and then gone in motion to be in, he's in motion or re-set. There aren't any others. If after he goes in motion he's "jogging in place", he's still in motion under the rules.
The only AR that I can find on the subject:
Offensive Team Requirements—At the Snap—ARTICLE 4 - Approved Ruling 7-1-4
I. A30, lined up legally as a back, starts in motion legally. He then turns so that he still is legally in motion but is facing his line of scrimmage using a “side-step” motion. At the snap, A30 is bent slightly forward at the waist and is either continuing his “side-step” motion or is “marking time” in place. RULING: Legal.