Bunch of thoughts on this:

1. Avoidance is a behavior pattern. And the more things you avoid, the stronger the pattern becomes. So forcing yourself to say "good morning" and to smile when you enter the office might be a good idea. But also be on the lookout for things you avoid before you even get to the office. The earlier in the day you can face your social fear and break through the avoidance pattern, the easier it will be.

2. Realize that others have the same fears as you have. It's just that they're just as good as hiding them as you are. All you ever get to see of other people is their exterior. But all the chatter inside their skulls, their pondering and their insecurities are hidden from you. Hence they automatically all look so much "cooler" then yourself (who is the only person on the planet whom you can never ever see without the constant soundtrack of his inner monologue).

3. Get better at "running human in emulation mode", as Elon would put it. This ties in with concept number two. The more clarity you have about the true motives, fears and desires of the people around you, the more helpful you can become. And being able to be helpful is the biggest confidence booster. Alfred Adler posited that "contribution to others" is the most important human need. So the best treatment against fear is discovering what you have to offer.

(An example is someone who is afraid of talking to the opposite sex. The cause of that fear is likely the feeling that he doesn't have anything to offer. The he is just trying to "get" something. But this interpretation is very one-sided. It is the result of "not seeing" the other person, and of being focused only on oneself. The fear dissolves as soon as he realizes that he has the power to make the other person smile, to make her feel good about herself, to make her feel "seen" and appreciated. As soon as that becomes the focus of the interaction, rather than getting something out of it, the fear disappears.)

4. Practice smiling. Most people (especially men) underestimate how threatening they look when they're not smiling - and especially when they are afraid. This is a thing that actually comes up in marriage counseling as well. If you don't smile, you trigger fear in the people around you. They will be just as afraid as you are - and thus you'll be creating proof for the very thing that causes you to feel unhappy (and unsmiling) in the first place, i.e. that nobody wants to have anything to do with you. Look at JFK. Try to find a photo of him where he's not smiling. It's quite hard. Now imagine I'd be sending out a photographer to follow you around all day and snap photos of you. Most likely, the difference would be dramatic. The most simple "hack" here is to simply practice smiling in front of the bathroom mirror. Do it in the morning after brushing your teeth. Consider it an investment in your social hygiene. Just like frowning, and just like fear, smiling is contagious. The more you smile, the more others will be smiling back at you, or start talking to you, or start liking you. Which, of course, will give you even more reason to feel happy. So it becomes an automatic thing. It's just that, when you've been working a lot with emotionless computers, you might need a little "priming of the pump", so to speak.