First I’d recommend going to a psychologist, if you can afford it. Not a psychiatrist, because they’ll most likely treat it with medication, and IMO shyness is a learned behavior, as is social confidence (no offense to any psychiatrists here). Any psychologists here can better explain what may be going on mentally here.
That said, some tips. Find some interests, the more, the better. People like to talk with others about mutual interests. Explore those interests, that is how you’ll meet people with those interests, and you can practice talking with them.
GET OUT. Get used to being around people in public. If you don’t have a group of friends you can or want to consistently go oth with, go out alone. People who are alone are very approachable. Plus, counter-intuitively, I’ve found, it makes you seem MORE socially confident, as in, you’re not afraid to go out alone. Most people are.
Be nice, and be relaxed. Smile, and call the other person by name. Someone who’s nice and relaxed and smiling is easy to talk to. Let the conversation flow. Ask questions, seem interested. If it doesn’t seem to be going well, bail.
Get used to rejection, and don’t let it bother you. This is much easier said than done. Many other people are shy, and will have just as much trouble talking with you as you are having with them. Also, people are busy and preoccupied, and just may not have the time to talk. As you practice meeting and talking with people, eventually it won’t seem like such a big deal if you get blown off. Just tell yourself that there are 6 billion people in the world, and it won’t be hard to find someone else. Also, as you talk with people more, you’ll start to learn who to avoid, and who to talk to, and how to talk to them, etc. Plus, you’ll begin to realize there’s always someone else to talk to.
It takes time, but it can be done. Eventually it’s easy. Hope this helps. Good luck.