Air carrier pilot reported during taxi in to gate; ground personnel drove a baggage belt loader into the the safety envelope and ramp area; requiring the pilot to stop to avoid a collision.

Narrative

We were approaching gate XX at ZZZ. Both wing-walkers were in position; the DGS (Docking Guidance System) was correcting registering our aircraft (A321); and the ramp area was clear. Just before I entered the ramp area (approximately 50-100' away); a ground personnel driving a baggage belt loader started backing away from the aircraft that was parked at the gate to our left (XY). The driver did not seem like she (could have been a he) was aware of her surroundings as I did not see her look behind her as she was backing up so I stopped the aircraft. Sure enough; she backed right into our safety envelope; then proceeded to drive forward and make a right turn back into the XY ramp area. During this entire time; she was behind our left wing-walker so I don't believe he saw her until I stopped the aircraft. If I had been further along in my taxi in; where she was no longer in my field of vision; she could have backed into our aircraft or run over our wing-walker.Cause: lack of ground crew situational awareness. Recommendation: Train ground personnel to look behind them when backing a vehicle; including consideration for what may be going on at the next gate over.