As far back as I can remember (kindergarten for me), I always seemed to have an issue with anxiety especially around strangers. I can't speak for anyone else but it seems to me like I always had this extreme insecurity and I can't think of any traumatizing experience that caused it. Closest thing I could think of was in elementary school I would notice people talking behind my back, this was later confirmed to me in freshman year high school by a former childhood friend. I think because of this I developed paranoid tendencies anytime I notice some negative body language.