It’s normal if they are usually home. My LO started interacting and play herself outside only after 1.. Cause when they make eye contact with another stranger, they are scared. My LO can talk whole day non stop but once she’s outside and see strangers, she becomes silent mode. Now she can wave and flying kiss to random strangers (although 90% of the time she gets ignored and feel sad). Interact with older kids and even approach other parents to play. Try bringing baby out more, don’t force them to interact when they are showing refusal. Let them slowly open up and explore. It will get better overtime when he’s used to seeing more people outside.
same as mine