Why do I get nervous and scared when I give a speech?

If you're afraid of talking in front of an audience, it may be due to the spotlight effect. You feel uncomfortable in the spotlight. This is likely due to something that happened in your past. Maybe you made a mistake in your past, or you were scolded while you were speaking, or something like that. So this gets patterned into your nervous system. One of the first things that needs to happen is for you to get comfortable making eye contact, comfortable with people looking at you, and comfortable with talking while making eye contact. You can practice this just be being mindful of this while you're talking to groups of people and strangers. With practice and mindfulness, these feelings should go away over time.