It takes an action to don and to doff a shield (See Pg 146 of the PHB).
Does that action need to be the PC's action, Or, could another member of the party (another PC), or even a familiar with opposable thumbs (eg. Imp, Sprite), spend their action to remove a willing player's shield?
Example: P1 is wedged under a boulder. P2 needs P1's shield. Can P2 remove P1's shield as an action?