Just waiting for that elusive moment of energy+motivation.

Quite often I see really relatable things in neurodivergent communities and go “surely that’s just something everyone does”, but now I’m starting to wonder at what point one ought look into things.

Don't wonder to hard, many of the things discussed are common and not necessarily a disorder. And when they might be it's often paired with the wrong disorder (this would be depression, not really ADHD for example). Take most of these meme and a humor communities with a giant grain of salt (or skepticism).
- That's patently incorrect. Executive dysfunction, a hallmark of ADHD, often results in something called "task paralysis" wherein you're unable to begin a task, even though it weighs on your mind.
  
  The advice that a person could be exhibiting this symptom because of a different cause (such as depression) is true, but people with ADHD experience this issue at a higher frequency than their more neurologically typical peers, and if it's a problem being caused by ADHD, and not depression, it can lead to depression as a comorbidity.
Pretty much all symptoms are on a spectrum that also includes "normal". If it happens significantly more than everyone else and is clustered with some specific other related symptoms, a professional might give you a diagnosis, but I wouldn't worry about it unless you get to the point that you feel that you need help.

Also, there are way more disorders than measureable symptoms, so there's a lot of crossover from various causes. For example:

Does person have trouble focusing because of ADHD? Or could it be depression fog? Exhaustion from anxiety? Sleep apnea? Chronic poor diet/fitness? Work burnout? Etc...
- Yeah I don't think too much about it, I think most of my quirks can be boiled down to me just not being properly socialised; I moved around and changed schools a lot, coupled with being an only kid with an abusive mother, it's a recipe for some stuff getting fucked up. It can be pretty debilitating; I get super anxious in large groups of people (earplugs/noise cancelling earphones help) and I can't really deal with social gatherings for long without crashing. My solution is to just not; I work from home and keep to myself and it works pretty well.
  
  Something that did catch my attention once though was someone talking about their experience with audio processing issues. Someone will say something to them and they hear that someone says something, but they don't understand it. Or they say "what" as they're still processing it and then respond right as the person repeats themselves. I always thought that was particularly strange as I have really sharp hearing, and I never felt like I didn't hear what someone says, it's more that I didn't get it or I hear them say something they obviously didn't say.
  
  In the end I'm not too bothered though. Currently I'm perfectly functional and mostly happy the way things are. I'd be pretty fucking upset if someone started mandating that I go to an office daily, but I'll burn that bridge if I ever end up at it.
- Is "literally every time I need to call someone" the normal amount?
I was thinking exactly the same

I was so proud of myself a couple years ago. I did my taxes in late January, shortly after getting the form from my employer, instead of waiting until April to do it. Then, shortly after that, they gave out another stimulus check (last one I believe). I barely didn’t qualify with the income I submitted with my tax paperwork, but would have qualified if I had waited until later to file my taxes because I made less in 2019. Now I’m back to procrastinating doing important tasks, because that step of locking in my choice “early” might come back to bite me somehow…