But why is it moving should be a question.? . . . Is it just the inertial movement from stopping etc while fast jogging or is it from vibration.?

If it's inertial then it's simply the lack of mass but if it's vibrating or shacking from miss aliagnment then you need to find the cause because even if it's fastened to the wall floor while it won't walk around the floor it will still resonate and show in the finished cut. . . . It will also destroy it's self in a short amount of time if too bad.

It's not uncommon for small or light framed machines to walk around while rapid jogging so nearly always need bolting down. Even my steel framed machine is bolted down.