Why do I dare to sing when I am alone, but I can't sing when others are around? How can we get rid of this situation?

The reason for this kind of psychology is nervousness, fear of making others laugh by singing wrong, in other words, fear of others having a bad impression on themselves.

Actually, just sing boldly. What others say is someone else's business, ignore it. On the other hand, even if others laugh at you, treat it as a pleasure and don't take it seriously. No one laughs at you every day, just for a moment, and soon forgets.