Even if you have the most confident, beautiful singing voice in the world, you may feel nervous if you aren't ready to perform. Feeling pushed into a tight spot where you don't have the tools to succeed is a frightening experience. For example, performing on the spot may cause you to blanch and feel butterflies in your stomach. You may also feel nervous if you didn't have enough time to memorize the tune or lyrics of a song.
Some people tend to feel they aren't good enough, which can lead them to feel uncomfortable with other people. Sharing your voice with others may seem like an impossible task if you don't believe in your talent. These feelings of insecurity may come from the taunting of peers or simply from an insecure mind. This nervousness may be groundless, but it is still difficult to overcome for many people. You need confidence to sing well -- and confidence comes from within.
Some of your daily activities could affect your performance. Caffeine and medications can make you feel edgy and nervous. Lack of sleep can also make you feel nervous and stressed before a performance. Low blood sugar due to lack of food is another culprit that will make you feel lightheaded and fidgety. Cut out caffeine, eat a healthy diet and get plenty of sleep to prevent nervous tremors during show time.
You may be an experienced performer with some people and a shy person with others. It all depends on your relationship with that person. For example, if there's someone in the audience you are particularly fond of, it may be hard to sing confidently. Despite your desire to show off your natural talent, it is tough to express yourself through singing when someone you are nervous around is in the audience.