Self employed. My husband and I own a commercial cleaning company. Currently sitting outside a car dealership where I clean by myself at night. No one is here and it's great! My husband is extreamly outgoing though...

Electronics/manufacturing engineer.

I spent some time as COO because that’s what the company needed. During that time I tried to manage sales people.....it was a living hell.....I am soon going back to engineering and look forward to being alone for long periods of time while working on complex/non-human problems.

College Professor.

I was a telephone operator when I was 16. Left highschool at the half day & got credit for working. Had to keep the grades up for this privilege. After 6 years I bailed. The minimum wage back then was 75 cents per hour. I was making $1.95 with benefits. Union YES! But I was too young to continue to do something I loathed.
I was a bartender for 10 years after that. Somehow the bar kept me feeling autonomous & safe with the ability to linger with interesting cliental & find other duties when wanting to escape a customer. Then too I was able to party safely.
I then became a telephone installer realizing I wanted stability at around 30 years of age. Bailed on that as I was unwilling to go into strange men's abodes alone. Transferred to customer service where people blamed you for everything. That was it . No more phone company.
So I became a botanical maintenance engineer. My term. I had a different route every day traveling around & taking care of rented plants in various venues. I submitted a ledger thru the mail, got paid thru the mail, but it was interim as it did not pay or provide any benefits. It was great tho. I was on my own most of the time accept in places like offices. The rolling rink was great, the hot dog stand, Northwestern University with the telescope, private mansions, a penthouse.
I retired from the USPS as a mail carrier at 53. Best of times. Worst of times. Pay parity, great benefits, physical work out, lots of dogs & cats, wealthy suburb, on the lake, wildlife & some very generous postal patrons. Celebrities & millionaires. But it was a men's locker room which resented women or harassed them. ("'Hey Johnny! What did Popeye say?" "This pussy is finger licking good'" Then there was Mr. Big shot who referred to me as "that little girl". I was 44 years old. Big mistake Mr. Suits. He was fired for getting caught banging a female clerk in a postal van. Tho by not playing the menstrual card, carrying my weight literally (required 75 lbs & I weighed 85lbs) & going toe to toe with insults, I incurred the respect of war veterans which says a lot. I was imprinted by boys my 1st 7 years of life so I know how to play it. Then after the postmaster who hired me retired, the white collar manager wanna beeeeezzzzzz came in seeking promotion via harassment of the weak & helpless. The target they put on my back after destroying others lives, was an error of judgement on their part. I took 4 of them down after they fired the 1st shot. One of them was arrested for fencing stolen postal property out of the office. Another developed ALS & croaked. Another was busted to janitor. Another was arrested for stealing $15,000.00. Nice managers huh!?I learned a lot from those war veterans. Knowing the regulations, federal law & the contract with the NALC inside & out enabled me to prevail. After 23 years I dropped dead from an asthma attack due to years of exposure to 2nd hand smoke. Survived the grim reaper & took those 4 aces the gods dealt me & exited with my integrity in tact along with the service awards I won. Used up my saved 5 weeks of vacation time & 6 months of sick leave. Did nothing for 7 months but get well on their dime. & then retired. Laughing last & living large ever since. I love the postal service.

I'm a software programmer. I work in solitude. It's great.

Most college professors are introverts. I'm among them.

Industrial Maintenance. 90% of the time i get to work alone. Just me and whatever piece of equipment is broken. The other 10% is hunting down people that submitted repair workorders or talking to operaters trying to find out how/why something broke. The plant is pretty damn large, so when Mr John Doe puts in a workorder and just says "airline broken, or Machine not working" without a site location or a phone # it flippin grinds my gears. Had to hunt your ass down, charging your department for that time too!!

I used to be an electronic technician before I stopped working; very handy with an oscilloscope and multi-meter. Human contact was mostly in the form of written or on-line fault reports or instructions to reworkers on what components to replace.
Most other communication was with a pcb or device itself in various ways.
"Good morning, how are you today?" (runs diagnostic).
"Your output is slightly down, let me check your power supply". (Applies multimeter to test points)
And so on.
I've done this sort of job and others requiring understanding of electronics for most of my working life and found it very rewarding.
I had never thought of myself as an intro or extrovert before I met and got quite close to a very extroverted lady. At the time I was interested in a computer language called Python and found that she could not understand why I would want to be concerned with such a thing.
I'm not a total recluse, I do like to meet and talk with people, but usually on a one to one basis in an atmosphere of peace and quiet.

I already shared that I am a published author, but (so far) that's not how I earn a living.
I don't want to share my profession at this time. I don't want anyone rejecting me because of my income which they have estimated by my job title. Likewise, I don't want to date someone who is attracted to my large, steady income, instead of being attracted to me.

Oh boy. I'm a mental health and AODA therapist. I like those interactions. Other than my kids, don't usually enjoy hanging out with people during my free time.