I need to disconnect from social media in order to relax. You would use the word disconnect in this virtual scenario, not physically/in person. For the latter, you could say that you need some ‘alone time’.

Yes! Actually, people do use the word in this exact way. Only thing is that, like Rohan said, you would probably say something like "disconnect from social media" (or social situations) than "disconnect" from a person. Like if you said "I need to disconnect" to someone, they would probably understand that you mean you need alone time. It wouldn't sound weird. If you said "I need to disconnect from you" (or if you make any reference to people) that will sound really weird.