Question about pain/musculoskeletal shoulder pain [Ask CashDoc]

[Ask Cacidoc] I have a shoulder pain inquiry~ These days, I think I sleep poorly, so I have a stiff neck and pain in my neck, shoulders, and arms. When I perform the motion of scratching my back, my shoulder hurts even more. I'm worried whether it's due to aging or because I don't exercise well, and whether physical therapy helps improve the condition. I can't move my arms freely up and down, so my daily life has become very inconvenient. What are the causes and treatment methods for shoulder pain? If there are rehabilitation exercises I can do in daily life, please let me know.