I'm sure that even some professional musicians have that nervousness.
Read here: http://www.benedictroffmarsh.com/prollrec.html
Read more about this plugin. It may work for you.Many musicians and singers clam up and go all gummy as soon as they know that the big flashing red light goes on. They can run around like idiots in front of 20,000 people and be comfortable but as soon as they know that the engineer has gone into record they cease to be truly emotive. An old trick was that the engineer would be sneaky and record practice runs without the artists knowing (even going so far as to break the knob off the recorder so the red glow couldn't be seen) in the hope of capturing the real soul of a performance.
Good luck.