I really hate my MRIs, I get super claustrophobic too. I always ask them to put the mirror on the ceiling so you can see out - it makes me feel calmer focussing on the doctors through the glass doing their thing. If you don't sleep tonight, don't worry - even if you are tired tomorrow it will still all be fine.

I used to be very nervous like you, but after dozens of them I have a system: I make sure the staff put on my relaxing pop music (in my case it’s The Best of Phil Collins - he’s not my favourite or anything but his music is just the right amount of happy-without-too-much-thinking). After getting used to hearing that familiar music start (I don’t really listen to it outside of an MRI now) my body automatically starts to relax because it subconsciously knows it’s lie-down-happy-time. I have even dozed off a couple of times! (Although snoozing is not advised cos your falling-asleep leg twitches can affect the scan). So I guess my advice is find some happy zone-out album, and give it time. It may take a couple of scans for it to work, but I hope it does work for you too. Hopefully I have been some help. 🙂