Does your dog tend to do this more during or around certain people ?
If a mature dog feels anxious due to changes in the household or routine, they may use humping as a self-soothing displacement behavior. humping mature
If the humping becomes compulsive or leads to aggression when you try to stop it, consider working with a professional animal behaviorist. They can help create a tailored plan to lower your dog’s stress levels and replace the behavior with healthier habits. Does your dog tend to do this more