Why do I fear intimacy and affection?

There’s a girl that is best friends with my cousin’s girlfriend that my cousin introduced me to. I’ve met her only once. My cousin’s girlfriend is playing matchmaker I guess and told me that her friend thinks I’m a gentleman and is interested. I hardly talked to her the time we met in person. I have her on Snapchat and we talk on there, but nothing personal. I don’t feel emotions like most people do. She’s a nice girl and would like to take it further, but I just tense up and shutdown when I try to think of something to talk to her about other than about work and weather. I don’t know how to make a move. I was never taught how to interact with women. I do know the longer I wait the less interest she’ll have. Any advice?