Well, one common element is the lack of escape. Introverts often find themselves in situations where they can't easily get away. For example, at a family gathering where they are expected to stay for a long time and be social. Another is the fear of judgment. In many introvert horror stories, they are afraid of being misjudged by others because they are not as talkative or outgoing. And then there's the discomfort of being in the spotlight. Introverts usually prefer the background, so when they are suddenly made the center of attention, it's like a horror for them.
A typical element is the feeling of being overwhelmed. Introverts have a certain limit to the amount of social stimulation they can handle. So when they are thrown into a situation with too much noise, too many people, or too much expected interaction, it becomes a horror. For instance, in a big office party where they are supposed to mingle. Also, the sense of powerlessness. They might not be able to control the situation, like being forced to participate in a group activity when they don't want to. And the lack of understanding from others. People may not realize how difficult it is for an introvert, which adds to the horror.