I'm an introvert and I like going to work to do my job and go home. I don't understand people who use a job as a substitute for friendship or marriage. It's a means to an end.
The sooner I do my duties, the longer my downtime is going to be, and I love having my downtime.
Many of my colleagues see me and immediately start asking questions I don't want to answer, but neither do I want to hurt their feelings, I mostly want to be left alone. In the past this has been deconstructed as arrogance and people with fragile egos feel insulted by my indifference to them and that I prefer to work than to talk to them.
The world is made by extroverts. I have observed that people are eager to help you if you give them attention. I don't get it, but neither I'm not going to change how extroverts think or feel.
If I give them the attention they need for as long as they need it I'm going to end up with daily headaches and neither my job nor theirs is going to be done.
I want to appear approachable, but keeping the info I feed them to a minimum. How do I do that?
What do you talk about to your coworkers?
What do you say to stop conversation organically? (meaning they don't get offended).
The first is that you're introverted, and you need to learn how to communicate that to people in a reasonable way.
The second is that your workplace clearly encourages communication, and you have an issue with communicating. To some degree, you will need to adjust your expectations. You might think that your job duties are XYZ, but in reality, many of your bosses and coworkers think your job duties are XYZ as well as chatting with people around you, within reason. If you express your needs effectively, perhaps you can adjust that "within reason" to mean "less than now but not zero".