I’ll tell you the reason why many people experience the feeling of choking when they get nervous.
The small muscles of the throat do not have any kinesthetic senses that we cannot control by ourselves. When a person feels tense, the muscles contract toward the cervical spine. Consequently, this is the underlying reason why you experience a choking feeling in your throat.
Note:The voice is basically made by moving muscles. If you are tense, the muscles contract. Contractions cannot be controlled by the mind, they are a natural reaction of the body.
Even professional singers get nervous before concerts.
If you could try to enjoy the thrill of the nervousness feelings more, you can relax when you’re singing. It is difficult but not impossible. However, I recommend you acquire flexibility of your throat muscles first, this will assist in preventing your muscles from tensing at a high degree.