False Start or Illegal Motion???

[MD Longhorn]

I think the key distinction between false-start and illegal motion is suddenness. Think of it this way - if the player made a motion, consider what you would have done if, after making the questionable motion that you're flagging, the player stopped his forward motion and set for a second before the ball was snapped. If you'd have let it go, then you have illegal motion (moving toward the line when the ball was snapped). If you would have flagged it, then you have false start (simulating the start of the play).