People

I can say I recognize a bit of my younger self in this.
I found that my “erratic” acting in terms of varying personalty behavior, was because my awkwardness and lack of “understanding how to be”, made me act and project in a manner i thought was fitting to the appropriate situation or person I was with.
Sometimes it works, other times it bombs hard. What I eventually found was that the age old cliché “be your self” was true. At least to a degree, maybe not 100%, don’t be a dick just to be a dick, add 80-90% of yourself and 10% manners or such, since there will always be a bit of a decorum when interacting with others
While that can be difficult for several reasons, and one might feel and find, “this shit aint working people hate me when I’m myself”, that might be right, not all people like, attract, or interact with the same things in mind. For me, the pretending, acting, made me feel worse than the loneliness on its own, and still made me feel lonely when surrounded by people.
Being my “self”, might mean that my sphere got smaller because not all agreed with it, but made me feel better, by a ton, compared to being in large social circle, having to fight and act to please everyone to try and not be lonely yet feel more lonely than ever

What could help with this is group “therapy”, I say therapy in quotes because it doesn’t have to be actual therapy, group meetings, support meetings can work just fine.
But while it didn’t really take on me, because of my other issues, I did find that group therapy for social anxiety was what had the best/closest thing to an impact.
For my little sister it worked wonders, really helped her come out of the shell, and form some connections and find comfort in a few more meaningful ones, than a sea of meaningless ones.

It can be hard to get an idea of how to “act”/be around people, if you aren’t actual around/with people, a group can help learn and deal with that, because the focus will be on that.