OP - i actually understand.
I hate making phone calls or talking to people in general, and never know what to say. (I am so much better in a text or email.) And it seems the longer I put it off, that's just another reason to not want to call - to explain why I put it off and then to say what I didn't know how to say initially. I am this way in so many situations - when something tragic happens, when someone . I
Years ago, my lovely SIL had a late miscarriage and when her husband (DH brother) let us know, we offered our sympathies; but I kept putting it off calling her because I didn't know what to say. I was talking to a friend a couple of weeks later and she said I should def reach out , and that it would be more awkward when I finally see her and not have ever called.... So I did. I just said "hello... I'm sorry" and my SIL took over the conversation. She expressed that she was waiting for me to call

And then she just poured out the details of what happened and how she felt. I just listened, and then told her i was there if she needed to talk.
You've gotten great advice here. Just want you to know that I understand anxiety over these situations.