I have a lot of anxiety and I am scared....
That first step onto the mat is always the hardest. Once you do, the feeling gets better and you'll love it. The instructors know that it is intimidating (they were in the same shoes many years ago). They have many ways to make it less intimidating. after a few minutes, you'll be having alot of fun.
MA training is a journey of a 1000 miles, and it begins with a single step.