I had a similar experience (which I tried to "solve" in high school via World of Warcraft), and honestly I see this more in my case as a manifestation of depression, not pure boredom. Often the issue was that nothing SEEMED interesting/worth doing, and once I got started I'd be ok, but the initial push to get started was too much effort, or I'd stop too soon and wouldn't be able to get fully engaged with the activity.

I was just thinking about it last night: I went for a run, which is a little unusual for me, and I was similarly "time free" as most nights but a lot less bored. I felt my ideas/internal state was more interesting/entertaining, perhaps due to changes in my neurotransmitters caused by exercise.