Most people begin to stutter before their adulthood, but it can develop later in life as well. However, I don't think your problem is of the permanent and lifelong variety. I would recommend speaking with a speech therapist. Even if you don't chronically experience stuttering and/or blocking, a speech therapist may be able to help you develop techniques that will allow you to work around this hindrance until you regain your confidence in your vocal abilities. EDIT: spelling