I’ve never had a group interview myself, but I know people who have.
Generally, everybody is all in the same boat. You’ll get a few that are quite confident and have done this type of thing before, but you’ll also get those who are more nervous about it, perhaps because it’s their first time.
A good tip is just to be confident and don’t come across as shy or overwhelmed by being with other people. You will get the chance to know the other people a bit better, and you’ll probably do some group activities to see how you work with others and what kind of things you are capable of.