Below are a few things that I had found helpful:
1. Book "Human Relationships" by Steve Duck . The author of the book says that his students were suffering from the same people/relationship issues as everyone else in spite of the relevant education in psychology. So he reasoned something is all wrong about the way social psychology is taught, and wrote this book for helping people as oppose to teaching them. One impact on me was learning that the percentage of people feeling shy about initiating a conversation at some point in their lives was nearing half of them. In other words, the person in the front of you could also be just waiting to talk to you. I had read the first edition of the book which had very natural tone to it. The fourth edition  seems much refined for rigor, which seems impacting the basic premise of the book! So consider buying an older edition.
2. The challenge for me wasn't just difficulty in talking, but a limitation of interest and knowledge outside of the STEM fields. This then becomes a vicious cycle since you would not talk to people and not even learn about topics outside of work. Build some common interests outside of work, may be just by reading some books in isolation. Read a lot of news, as a lot of conversations build on it.
3. Early on, I used to be the silent one in many conversations because of #2 above. I started participating in the conversations simply by asking questions on what I did not understand. Asking too many questions annoys people, so need to be balanced. Read about the discussed topics offline afterwards as needed. Over the time, you get to understand those conversations, will start participating, and also, those people would start accommodating you while calibrating themselves for you with the skill level you have.
4. The people around would accommodate you, as far as they do not see it as your lacking interest in them. It's better to be seen as a person lacking people skills rather than as one lacking interest in them. Try not to miss lunches and dinners opportunities at work, even if you are not talking much there.
5. One-to-one conversations are easier. Break the ice with those. Soon you would be comfortable in a group setting where you are comfortable with say half of the people.
6. Join social media and make connections with all those people. Being behind a keyboard instead of face-to-face helps because you get more time to think how to respond. Do genuinely participate, click Likes, etc. This will not only develop connections with those people, but also slowly make you better for live verbal conversations.