I have weird urges to do shocking things in public and then I imagine people's reactions.?

I have really sudden weird urges to do shocking things in public and then I imagine people's reactions. After I imagine how other people will react I get really nervous that I may actually do the thing that I'm thinking about and I feel like I need to consciously restrain myself. For example, I was in biology cl yesterday and all of a sudden I imagined myself jumping onto the table and screaming "YOU'RE RETARDED" at my teacher. Then I imagined how the teacher/ other students would react. Then I was overcome with the urge to do this and I got nervous because I felt as if I couldn't control myself. I become overwhelmed with paranoia. It dies down after a few minutes. Is this normal? Do I have a mental/psychological problem?