Hey, John,
Many authors have said "You can't edit a blank page", so all credit to you for getting down your first draft. I mean that most sincerely. Filling the pages is the hardest thing!
Is this your first paragraph? Or is the whole book written. I ask because you might do better to write at least the first 100 pages before you try to edit the first one. You could waste years, and then some smart-*** will point out that most authors end up throwing away the first 3 chapters, and starting with Ch 4!
Eeeek! Right?
It happened to me.
When you are ready to submit to an agent or editor or contest judges, the first five pages have to grab them. The first line of a chapter isn't called "a hook" for nothing.
A good story often starts at a climactic point when someone's life changes.
A sore neck sitting at a computer is metonymy (the part stands for the whole). It's a well accepted literary convention, like all "hands" on deck (you want the attached parts too), or being fond of the bottle (or its contents). However, it isn't very immediate.
Some literary agents (I won't name the one I have in mind) don't like the use of the third person (He/his). It's hard to identify with an anonymous "he".
Would "interactions" work? "Social intercourse"?
You may not want to talk about "random happenings between people" at all.
I think you need to be specific. You need some dynamite.
Even if you are not going to use the scenes your hero recalls or imagines, you might write them to clarify what you are talking about for yourself. Is your hero writing about hook-ups, collisions, exchanges, road rage, jay walking, being pestered on the street, parties, loneliness...?
Sincere best wishes,