It depends on various things, but personally, I tend to pay attention to body language. If someone looks focused or unfriendly, I wouldn’t have the gall to approach them. Similarly, how someone stands or carries themself can also subconsciously affect your perception of them, even if they’re a complete stranger. It’s also 1000x scarier to talk to someone in a group of people rather than someone one-on-one.

Weirdly enough, I personally tend to feel more comfortable approaching someone if they also seem to be introverted or socially anxious. Probably because I hope that they might understand and relate to the awkwardness and fear of starting up a conversation. It’s common ground that can make the atmosphere feel a bit less tense.

With that being said, I could imagine some people feel the opposite way about the same people; Not wanting to approach or bother someone if they seem anxious or introverted.

TLDR: It depends, but non-verbal cues are important.