Someone else recommended this to me; try box breathing. You basically just inhale, hold for 3-4 seconds, exhale, hold for 3-4 seconds and repeat. It’s actually helped me and I hope it helps you too

It sounds silly and it’s not realistic for 5 hours straight but when I had an MRI I just closed my eyes really tight and imagined I wasn’t in such a small box lmao

looking out the window and focusing on the outside of the car helps me

the MRI thing, yes !! when i had one they asked if i'd like a towel over my eyes so i can't see the tight space i'm in and it really helps. you could get a sleep mask to wear over your eyes and just put some headphones in. do it as long as you can and maybe even fall asleep the whole time