Why am I socially confident only when I'm with a close friend?

Name: Aditya Date of Birth: 27 June 1997 Place of Birth: Bhubaneswar Time: 8:45 AM. I've realized that I'm perfectly fine in social situations if I have a close friend accompanying me. I can talk, laugh, and even give presentations in public if they're with me. But as soon as I'm alone, I get vulnerable and anxious. I don't make eye contact, struggle to talk, and feel like the world is judging me. It's annoying because I know I can be sociable. I just need someone with whom I am familiar nearby. Why does this occur? Is it dependency or a kind of social phobia?