An Introvert Spasm is when a person with an introverted personality suddenly cannot handle interaction with other human beings. It seems to happen suddenly, but this is deceiving. In fact, an introvert spasm takes time to build up in the introvert's system before is spasms out. While the introvert might not notice the symptoms of the building up process, it's been documented that after the introvert realizes what's happening, they can note the symptoms and be in a better position next time to avoid the complete spasming effect.
... until then.... I will continue to have my introvert spasm.