Hi! I am almost 50 and still have this same problem answering the phone. When I’m not expecting a call it’s totally fine. But, as you said, when I am thinking about it and expect to not speak, sure enough when I go to say hello absolutely nothing comes out of my mouth. So embarrassing and I totally understand. Another time it happens to me is when I’m in a store and the clerk asks me what my name is to put clothing in a fitting room and sometimes I just look at her with my mouth open and nothing comes out. I have to pretend cough like I have something stuck in my throat. Usually everyday speaking is fine except for the words that start with ~br So I have to think of another way to introduce my brother!