The jitters can be jolting — and so memorable that you'll do just about anything to avoid that awful feeling. The good news is that nervousness can be tamed. And, some sense of anxiety before a "performance" isn't a bad thing. You're likely to be uneasy because you care a lot about what you have to say, and you want your words to come across in a way that your classmates can understand and appreciate.
When I am making a speech or a presentation in front of the class, my face or body automatically shivers. My voice gets weird also. How can I stop it?
What we call "stage fright" is a common condition. Even famous people who have been speaking, singing, or acting in front of audiences for years admit to the symptoms you describe — and worse. They're afraid they'll draw a blank, squeak out words in a funny voice, trip and fall, or otherwise humiliate themselves in front of a crowd.
One way to calm your fears — and to settle your body's quakes — is to be fully prepared for your presentation. Do the homework, and practice, practice, practice. Dress the part. Get some rest and look your best on the day when you'll be standing up there. Give your body some fuel to go on, too. Eat a light meal or snack that can boost your brain power. You may tremble if your system's trying to track down resources to support all that stuff you crammed in your head.
Keep in mind that everyone in your class experiences a taste of panic when they're called upon to be the center of attention. You can help them out — and set a good example — by listening to their presentations courteously and with a pleasant expression. Who wants to look out into a classroom of bored or grumpy faces, anyway? Maybe they'll return the favor when it's your turn center stage!