Team A must have all 11 players (or less) in a legal alignment and set at some point before the snap. If a team A player is in motion at the snap and the entire team has not yet been set at some point prior to the snap that is a foul. The call would be false start.
Rule 7-1: Shift and False Start
ARTICLE 2. a. Shift. After a huddle (Rule 2-14) or shift (Rule 2-22-1) and before the snap, all Team A players must come to an absolute stop and remain stationary in their positions for at least one full second before the ball is snapped, without movement of the feet, body, head or arms (A.R. 7-1-2-I).