I believe hyperfixations are short intense bursts of obsession with something. Like right now I have 10+ tabs on my phone (which I almost never use for internet) dedicated to ski stuff, I searched hard for a good, affordable opportunity to go for hours straight and went last night, if someone let me I'd talk for 10 hours straight about mountains and snow and avalanches and weather and the differences between camber and rocker and edge angles and why Vail sucks and touring and places I suspect there's good backcountry, etc.. I'll get angry if the day after it snows I had an appointment in the middle of the day. The thought of it brings this focus and a kind of high. But three days ago it was learning a specific piece on violin I was fixated on (and forgot to eat or go to the bathroom while working on it), and all of a sudden in a second the boredom sets in and "oh, okay, yeah, cannot do this anymore."