You are what you think. If you are nervous around people you'll make them feel uncomfortable. The easiest way to get strangers to warm to you is to ask them about themselves or pay them a compliment. People like others ba<x>sed on how that person makes them feel about themselves. Also, finding common interests is a great way to turn that stranger into a friend. Most of all it takes practice and even then not everyone will like you, but those who do may grow to love you. Good luck :)
Its not just you. I feel the same. You always wonder if you could find a intrest that you have in common or if they will make fun of you. Its all about taking the chance and getting it over with.