The best way to answer this question is to think about the most welcoming and friendly people that you have met in your life - part of being a medical professional is interacting and helping many different people and it is key that you have an open and inviting demeanour. Part of this includes smiling, open body language - you are more likely to think positively of someone if they are welcoming and friendly towards you. Depending on the context of the interview, it may or may not be appropriate to shake their hands - in times of COVID it may be best not to, but the most important thing is that you are smiling and open with them. You have nothing to fear, and allowing yourself to be open lets them see your best characteristics and really let your personality shine.