Relax. Easier said than done, I know. But really, the best way to tackle interviews is when you're relaxed. By being nervous you're going to think of everything that can go wrong, instead of thinking of everything that can go right. Once you've done that, I suggest going on Youtube and looking at Kevin Ahern's guide to acing a medical school interview. It has 2 parts, and they're hugely informative on how to take control of the interview. (Though this may be largely irrelevant since interviews are now online) If you're in control, then you won't be nervous!
I've conducted many interviews myself, and let me tell you I was almost as nervous as the person I was interviewing! When I was doing interviews, I looked to see if they would be a good team player, direct, creative, and how they would tackle certain scenarios. I wanted to get a sense of who they were, and if I could work alongside them. Of course, medical school interviews will be a little more in depth, but hopefully this puts you more at ease.
A lot of people say to "just be yourself" and yeah they're not wrong. But that's very hard to follow with high stakes for most people. I suggest that you interview other people and take it seriously as if you were the one who was the gatekeeper for medical school. What characteristics would you look for? Do you want them to be humble, direct, a team player? By doing this, you'll understand how to just be yourself in your own interview. Not only that, but you'll know what the interviewer is looking for... because, well you've been in that position!
Just my thoughts.
