I'm very introverted and it would be very unusual for me to be confused with an extrovert. I think when I feel like I am being very outgoing, I seem "normal" to other people. It only feels exuberant to me. If I am really connected to the moment, then it has an intensity that can make others uncomfortable. I think an introvert may have a harder time balancing their energy - it comes out inconsistently.
Since I was young, people have commented that I am very quiet, but those who get to know me well forget I am shy & would not call me "reserved". My childhood ENFP friend would get frustrated with me because she didn't see me as shy, so she thought my reluctance to interact with people was snobbishness.
People exhaust me. Extended interaction for me can be anywhere from 10 minutes to 2 hours, depending on the intensity of it. If I can have moments of pause, then I can last longer, but after around 2 hours I tend to peter out.
I have this feeling of being freed when leaving a social situation. Like, when I am in my car driving off, I feel excited to be alone again.
I'm preoccupied with my own thoughts & exploring my inner world, and that's when I feel most at ease.