Perhaps he is just happy with his own company? I am a bit like that, I love seeing friends but I need time to recharge alone or just with my immediate family afterwards. My eldest can be like that too - he regularly sees friends at all his sports training (every weekday evening, and at comps at weekends, different friends at different sports), but if we have been say down at the beach all day with his friends from surf club, he will need a few hours to just be by himself before going out to train that evening. My youngest is a massive extrovert and would be with friends all day every day without a problem 🤣.
The only thing that would worry me from your OP is the fact that you said he spends all day sleeping, scrolling or watching tv. That’s a lot of screens - does he not have a limit on his phone time? I have 15 and 12 year old boys and they have 1 hour on their phones a day (they aren’t allowed any social media or YouTube ever), so they use that time to WhatsApp friends and/or play games. I do allow them extra 15 min bursts on WhatsApp if they are trying to arrange something with friends but otherwise they are off their phones most of the day. It means they have to find other things to do - sometimes with me, sometimes with friends (or a mix of the 2 if I take them and a friend out somewhere), and sometimes alone. The 15 year old is much much better at entertaining himself, he likes mooching about the farm on his bike, woodworking, going on the trampoline, practising sports on his own, going for runs, walking the dog etc. The younger one struggles by himself (perhaps because of being an extrovert), so he either plays with his brother a lot, or does quite a few holiday sports training camps, and I do stuff with him too. Today it’s sunny but they have a swim comp later so I don’t want to take them out for the day. The eldest has done a bit of homework and is now outside somewhere on the farm, either helping with the hay harvest or making something I think. The younger one has just ridden his bike 2 miles to the next farm to meet a friend as he was SO bored.
With your son, can you reduce screen time, impose a decent time to be up and dressed the majority of the week and arrange to take him to do some things he is keen on - getting him outside will improve his mood and sleep, and keep him busy til he is ready to start meeting up with friends.