Change of behaviour

My little one has always been a very out going little dude. His just turned 1. Anyone could hold him he would be moving around everywhere play on the playground try play with other kids all ages. For about 3 weeks now he has changed completely will not let anyone hold him if I’m insight and his not within cm of me he will cry and cry. Wants me to pick him up and hides under my neck if there are kids or adults around. Even people he is familiar with. (He doesn’t go to daycare) Just wondering if this is a stage or anyone else suddenly have this happen Thanks in advance 😊🤍