Why do men get nervous when they try to talk to women and why do women get nervous trying to talk to men?

Not ever person gets nervous while talking to the opposite sex, it depends on you, your confidence, whether you're shy or not, and many other factors. There is not one mold that everyone fits into, so it's impossible to answer your question.

If you get nervous while talking to the opposite sex, you have to figure out why. No one else can tell you why.

When you first meet someone, there is a natural hesitation, along with nervousness, in bravely going forward, and putting yourself in a position to be judged. Any initial conversations will be filled with 'what if's'; for example- what if he's going to think I'm too fat/thin/tall/short. He too will be thinking, what if my breath smells like a hockey bag, and she notices I have two different coloured socks on. So many little thought 'daggers' get in the way of allowing that initial connection to be comfortable.

It takes time. But, both parties go through the same initial nervous phase, and the unknown, as far as how you will be perceived, makes 'breaking the ice' difficult.

Patience and enough conversation to gather your wits, and realize he/she is a nice person, will generally make conversations quickly fun and interesting.

Even if there is no 'spark', trust your instincts. This person may not meet all your expectations, but you feel comfortable hanging out, and you enjoy the company.

This person could also make you feel uneasy, or even creeped out, or fearful- all things that your natural instinct is telling you, and you should act accordingly, and not second guess yourself. There is probably more to be gained by moving on quickly, rather than second guessing yourself, and taking a risk.

OP continues to post in generalities - "all" white women, "all" asian women, "all" men, "all" women.

There is no "all" when it comes to people.