I kinda recognize myself in what you're saying. Especially the "looking through the window" thing
I asked myself: "well, after all, am I not disentchanted with every thing?" Is it not supposed to be the sign of release. Still I get bored, not all the time, but a significant part of the day.
My analysis is that actually there is attachement. I say I'm disentchanted but my mind keeps running here and there about different details of the past and future. And I think this is this constant functionning of the mind which makes the mind kind of dull, or bored, or tired.
Well that's just my opinion.
A second explanation, at least in my case, is that I think unconsiously I'm awaiting something which doesn't come, and this create this mood which is not true disentchantment (though I think it is not completely different either, because there's no more excitement about external stimulations).
Of course I'm speaking for myself, maybe some of this can explain a part of what you feel.