Not a therapist, but have a look (or better, have a professional have a look) at ADHD-PI. What you've said describes perfectly how I feel at work a lot of the time, and it's what I was diagnosed with.
I seem to have a finite pool for motivating (or more accurately forcing) myself to do work. And when that pool is empty, it's off to HN or Reddit I go. Frustrating, and I still don't have a solution yet.
Working through some non-medicinal remedies first (changing habits, setting up routines, etc). Not quite having the effect I hope for, but we'll see.
The consensus of what I've read is that most pharmaceuticals are temporary fixes, at least for adults. But that's just heresay from the internet, so I might be wrong.
And for the record, since they are always so highly advised, yes, I already have good exercise, recreation and mental reflection routines in place. :)
I seem to have a finite pool for motivating (or more accurately forcing) myself to do work. And when that pool is empty, it's off to HN or Reddit I go. Frustrating, and I still don't have a solution yet.
Hope this helps.