The present invention relates to a device (1) for automatic injection of a product (3) comprising a container (2), a needle (6) and a piston (7) and, - a housing (12) receiving said container (2), said container (2) being movable with respect to said housing (12) between an initial position and an insertion position, distally spaced relative to said initial position,, - a safety shield (8) coupled to said housing (12) and movable with respect thereto between a rest position, an activation position, proximally spaced relative to said rest position, and a safety position, distally spaced with respect to said rest position, -biasing means (33) for causing the movement of said safety shield (8) to said safety position, - triggering means (29) for causing the container (2) to move from its initial position to its insertion position, said triggering means (29) being releasable by movement of said safety shield (8) to said activation position, characterized in that said device (1) further comprises isolating means (24) for isolating said safety shield (8) from said biasing means (33) when said safety shield (8) is moved to its activation position.
