Now I'm older, and have less fear of people, it depends on the context. In a shop, if the checkout person starts a conversation, then I can chat along for a limited time, but will have limited patience, and will not be hanging around to chat.
Generally I need to identify commonality between a stranger and myself, and that rarely is possible when in many cases, the person appears to me like a plain unadorned hardback book cover.
I went to an event for people who share a particular set of skills and interests a few years ago. However, I'm not skilled at it, so despite having this interest in common I felt like I wasn't worthy of being there, and wasn't able to approach anyone to start a chat. I left the event for a walk feeling tearful. As it was a long drive I returned and stayed for a short while, but still had only the most limited monosyllabic conversation with one or two people, mostly avoiding everyone.
When out for a walk in the middle of the countryside, it's customary to say hello, so I do, but usually continue walking.
Things like job interviews are very awkward.