A nice tip I got recently from some RSD video. Your brain is wired to help you avoid embarassment, that's why it tells you to be quiet ant not say anything. Approach anxiety. But if you start saying something, if would be embarassing not to finish it, so your brain will then start coming up with stuff to say!

So if you want to talk to someone but are getting anxiety, you can start by messaging "hey,". And then to avoid embarassment you need to say something meaningful, so your brain will start working for you.