Hi OP - it is a common misconception that people with ADHD have to be hyper - but there is a kind of ADHD without the H which is 'primarily inattentive' ADD, often missed or mis-diagnosed because as children we are less disruptive. Also the rate of adult diagnosis is high as it was relatively unknown when we were kids. This is a description of some of the traits:
Core Symptoms of ADD/ADHD
Though each of the ADD subtypes has its own set of symptoms, they all share the same core symptoms.
A short attention span for regular, routine, everyday tasks (homework, chores, etc.)
Distractibility
Organisation problems (like having a messy room, always running late, etc.)
Procrastination
Forgetfulness
Problems with follow-through
Poor impulse control (saying or doing something before thinking it through)
Primarily Innatentive Symptoms:
In addition to the core symptoms, the unique characteristics of Type 2/Inattentive ADD include:
Difficulty maintaining focus
Tendency to lose things
Making careless mistakes; poor attention to detail
Complaints of being bored
Appearing unmotivated or apathetic
Being tired, sluggish or slow moving
Appearing “spacey” or preoccupied
I got to 45 years old thinking that ADHD meant being hyperactive, before realising and getting a very late diagnosis at the same time as my son (and it turns out everyone with ADD/ADHD will have their own mix of traits - my son has primarily inattentive ADD but has the leg jiggling).
It is a neuro-biological condition which means the frontal lobe is made differently causing problems with executive functioning (basically the stuff described above).
A useful metaphor I heard was that if you imagine that part of our brain as having a series of cogs that have to work together - the brain of an ADD'er has slightly faulty ones - the things that make the cogs come together and function can be the leg jiggling (or fidget spinners) or intense focus/interest on something/massive pressure (often work well under pressure having procrastinated to the point it is now urgent - then, boom - they deliver). But for the most part to complete every day tasks that seem simple and normal to someone NT can take SO much effort to undertake it almost hurst - which is really hard to describe (and mind-blowingly frustrating for everyone around you - sorry!).
It may not be ADD/ADHD but everything you have said chimes and there is such a lack of awareness (understandably - if it isn't relevant to you you wouldn't know!), hence all that blah above. Might be worth checking out anyway! Good luck.