I too am an introvert, and I definitely prefer night shift, to the point where I would not consider working days, even if it paid more (which it doesn't
) That said, there are still going to be situations on nights when you will have to step out of your comfort zone.
Someone above mentioned calling MD's, which is something I struggled with alot when I first started, but now am very comfortable with. What helped me with that was having all of the information necessary right at my fingertips before picking up the phone, that way when there are inevitable questions about why you are calling about this now, you have info to back up your decision making.(funny side note; as I am writing this, I am listening to the hospitalist gripe about a nurse who called her to report positive cultures, but then didn't know whether they were blood cultures, urine cultures, how many there were, or what the growth was...)
Another thing to be aware of, if you are working 7p-7a: there will
still be family there when you arrive at work, and they will
start calling you before you leave in the morning. Just remember that in this situation, you are the expert. They are looking to you for information, and empathy. They want
to hear your input on what their family member is going through... like someone above said, it's not like striking up a conversation at a party.
And, finally I would suggest that if you really feel that if your shyness, and difficulty working under pressure will hinder you in a high pressure job, maybe try starting out in long term care, or some other position where you have your patients for a long time, and really get to know them and their families. That may help relieve some of the awkwardness.