Great post.
I had many of those symptoms when I was drinking heavily, off and on, for years. Then I was trying to seek pleasure and intensity in all the wrong ways, which never truly worked of course and made everything much worse... Getting sober resolved it pretty fast for me in general, but I experienced isolated spells during ~my first sober year. This dynamic clearly varies between people.
I think what can be helpful to snap out of this state is to force it in the beginning no matter how we feel. Do those things such as physical activity, going to places we like, socialize with people we like even when we don't feel up to it. Simply going through the motions initially can help a lot in starting to change our motivational state, I think it's a more effective strategy than waiting for it to return before we start doing the things we need to do, used to enjoy, or think we would enjoy. This action-based strategy has perfect neurobiological basis, since the activities themselves can change out brain chemistry, while it's less likely to happen if we just sit and wait for it. Of course starting is always hard, but it's worth it. Of course if it's persistent, it's best to seek professional help.