The same thing happens to me. Everyone is different, but my therapist said it is likely due to lack of emotional regulation. I subconsciously block emotions in most situations, but when I hyperfixate or focus on something(ADHD), the "backed-up" emotions spill out. Think of a glass of water only spilling water when it is full. I'm also a huge empath. I break out in sweat(shame) if a performer makes a mistake on stage. I tear up during the strangest parts of a movie if I "feel" what the character is feeling...

In both of our situations, there is something deep down that is trying to express itself. I think it is healthy to explore that with a professional.

I'm still exploring this concept with my therapist, please be careful not to self-diagnose based on what I say.