Suddenly scared of people?

I’m looking for advice and also to see if anyone is going through something similar. My son (now 3) has slowly since the age of 2 developed an aversion to people. It started with him starting to not want to go into events with lots of people (even if he knew everyone there) but he would slowly warm up and be fine…but now its become kind of extreme where if anyone visits us in our home he will cry his eyes out and work himself up saying “I don’t want them to come” “I don’t want them to talk to me” etc and having a massive meltdown. Eventually (like an hour later) if one person goes into his room and plays with him he’ll be fine with that one person but only in his room and doesn’t want to leave. In another scenario he burst into tears because someone waved at him and he said “I don’t want them to look at me” Interestingly its in home / event settings. If we’re out and about e.g. grocery shopping and someone says hi to him, he’s fine? His reactions are becoming more and more extreme and I’m not sure what to do? Is this normal? TIA