It really depends on the University!
Mine were a while ago, but I had interviews at Aberdeen, Dundee, St Andrews, and Glasgow. The first three all did MMIs.
Aberdeen and Dundee had several stations in the same room, with a buzzer indicating when the time on that station was up. If I remember rightly, they also had rest stations incorporated. In Aberdeen they had about 3 stations in one room, in Dundee they were all together. St Andrews was actually more chill: separate rooms for each station in a quieter, office-like setting, and most of them felt like more of a chat (but they still used buzzers). I'd 100% recommend reading the uni's own advice, and look at the medic portal for classic MMI stations.
Normally, you'll go for some form of registration, then the group of you who are being interviewed that day will go to a room where you're given instructions. You might be here for a fair few minutes before they can actually set up, and you'll probably get name tags.
In terms of your anxiety, I know that just saying "don't worry" won't help at all, but if it's any reassurance at all I actually found MMIs much less stressful. Once you get into them they tend to be a wee bit more fast-paced, which makes it harder to overthink!
Wishing you the best of luck!