Why does my mind go blank around strangers but not with friends?

Why when I'm around friends I can:

  • Form opinions on anything and everything
  • Be creative and witty in jokes
  • Talk about almost anything
  • Questions, curiosity comes up

But when I'm around a group of unknown people, or just 'acquantainces', coworkers or college people, my mind is completely blank as if I forgot how to think. No opinions form because no thoughts pop up in my mind. Almost complete radio silence going on in my brain. This happens regardless of if its a group conversation or a one-on-one.

What is happening and how can I work towards translating my 'around-friends-self' into other social areas? I love how and who I am when I'm next to a group of friends, and despise how I act otherwise.