Your dog's incessantly rubbing his collar could indicate discomfort or irritation. Firstly, ensure the collar fits properly without being too tight or loose. If the collar is not the issue, examining your dog's skin for any signs of irritation, such as rashes or sores, is crucial. If you notice any, consider switching to a different collar material, such as nylon or leather. Additionally, you can try distracting your dog with toys or treats when he exhibits this behavior or tries using a calming pheromone spray. If any underlying medical issues are causing the behavior, speaking with a veterinarian might help shed light on them.