The twitching is typical, like I said. Not in the sense that every time you meditate, from now till forever, you’re going to have it. But it’s common enough in stage 1. There are also related things that can happen in stage 2, but they’re not quite the same. So I’d say that they might be gone by stage 2 and probably will be by stage 3. Your body will get over it eventually. Think of it as your body trying to adapt to doing this new thing; it takes some time to iron the kinks out.
Good luck with your practice! Let us know if anything interesting happens.
The first paragraph isn’t about vibrations. That’s just visual junk. Looking at it closely will make vibrations apparent.
The second paragraph sounds like it’s about vibrations. The rapidly-changing graininess is overlaid by another pulse, yes? How do you know that it’s a pulse, unless you can almost-sort of see the fluctuation from “nothing” to “something” to “nothing”? (In stage 2 the “something” is clearest, so don’t expect the “nothing” to be overwhelming.)
If you can’t label “pulse” or “seeing” fast enough, try “that.” If you still can’t do it fast enough, simply see the vibrations without being distracted, or count them. Balance just seeing with labeling if distraction is a problem. Re-read my stage 2 advice in the post.
I’ll be away for a few days, starting now, so you’re on your own for awhile. Sounds like you’ll be fine.