I know exactly how you feel, I get the same way, mostly everytime I get in the car, If someone;s with me I try to get them to drive instead, and even with that I get nervous but not as bad as when Im behind the wheel,
Try to keep your mind busy while driving, think of positive things and say to yourself "Im ok, Your ok, I'll get througgh this, nothing bad will happen, it will be ok, ill be home soon" Positive self talk can make a big difference, dont give the anxiety a chance to ta