In your comments some of you express the concern that when you are anxious you stutter and the more nervous you get the more you stutter. Sometimes you enter mental block.
Stuttering simply means your mind is working on overdrive faster than your lips could catch up. Take a deep breadth. Look to your left slowly and look to your right, take a deep breadth, smile and then speak slowly.
Here is another tip: Watch a recent motive: The King’s Speech.