Declining interest in being social after getting comfortable in an environment

I noticed this pattern that I always seem to be more social when I’m getting to know new people in the beginning of the school year but while in the middle of it, the amount of energy I have for social interactions decreases drastically. I don’t know why Im like this but it’s bad because I recently got intimidated by grad students and professors who I was at a mini conference with. Normally I’m okay talking to undergrads because they’re on the same level as me but I just completed panicked and mad social anxiety at that event. I was really dying. Like, the amount of energy I have to talk to strangers always seem to decrease drastically as I get comfortable in an environment. I know so many people in school already in my first year that idk why but it just seems like I have less energy. Idk what’s wrong but yesterday was really bad and even my friend said I was wrong for not networking with them since they do a lot of research and titles don’t mean anything so I shouldn’t be intimidated.