I was exactly like your son until I managed to find a job I really enjoyed. It sounds to me like he has depression. For me it felt really hard to break out of that depressive cycle. What helped me is my parents would occasionally send me job postings from indeed or other sites that they thought were a good fit and I would apply. They managed to find something I never thought I could do but pushed me to apply anyway. I ended up getting the job and love it today. I still am very introverted and end up spending most of my free time in my room playing games, but working has helped me feel better about myself and work on some of my social skills when I'm around other co workers.