I’ve had several head MRIs because I used to have a hemifacial spasm, or HFS. I posted about my HFS years ago, to share in case someone else had it. It is pretty rare.
I just closed my eyes and tried sleeping. Just go along for the ride. Think of the serenity prayer: you’re not in charge so just chill out as best you can and relax, take it easy. Bring earplugs. They do help.