What has worked for me, is to gently confront those feelings of nervousness - to allow for the person to experience reassurance and safety. "You seem anxious right now, is there anything you would like to talk about?" etc. Of course, that will do only when it is someone you have the kind of relationship with that it would not mess up boundaries. If this is not appropriate, or it does not help, another way would be to get some more space for yourself - "I'm sorry, I'm having trouble concentrating on ____ and I really need to work on it now. Would it be ok if I work alone in this room?" (Or "Could you help me by not talking to me right now?")

And of course, there is the internal monologue of "This anxiety is not mine. I am at peace. I am confident that I can handle the challenges that come my way. I release _____ together with his/her fears, fully and freely. I release him/her in love, to his/her highest path."

I agree with Wind esp. the second suggestion - these situations are like "energy exercises" so they're good for you in the long run. When I run into someone's weird energy I concentrate on sending them love, it works every time. Sometimes quicker, sometimes slower :-)

A nice plate of pasta,some avocado covered with a tangy marinara or a salsa verde,Usually does it.