I'm not a woman and never experienced this in eyes of a woman but i give you reasons that exist and happened to so many people. (you don't have to necessarily experience it to talk about it, you need to know it's psychology)
-Shyness / -A bad memory of previous relation / -Bad memories such as rape and insult - / -Inexperienced in dating and relationships / -Fear of being judged / -Feeling that "i'm not enough" / -Anxiety of not being liked / -That anxiety would sometimes cause the person to pretend her personality, which that sometimes brings another type of anxiety and disorder by itself, because she knows, it's not herself / -Self-esteem issue - / -Anxiety caused by the fear of small talks and deep conversations, because she doesn't know what to tell about her personal life, because she might feel ashamed of some parts and she feels busted if it comes up! It's anxiety attacks in advance and appearance disorder, constant insecurity about how she looks and if she looks good enough.
So many more . . .
