"Brain orgasm" sensation: what is it? Why do some people experience it and others don't?

Some people refer to this as "ASMR," or autonomous sensory meridian response. There is a ton of anecdotal evidence available here and here. My entire life, I have experienced this occasional tingly (or "warm and fuzzy") sensation in my skull, particularly on the right and left sides but occasionally in the back. For me, it feels almost like a radiating warmth or goosebumps in my brain, and it is brief (my longest was perhaps ten seconds or so). The vast majority of people in those comment threads indicate that it is brought on by the following triggers:

• soothing repetitive sounds, such as whispers
• teaching or being taught something, even watching video tutorials
• watching people perform intricate manual tasks

Some of the commenters indicate that it might be the simple release of endorphins, but it definitely does not occur with all other endorphin-releasing actions (like exercise, sex, or laughter). Does anybody have any explanation for this?