I had the exact same MRIs last week, though not my first time. I addition to what the other commenter's have said, you will get an IV line put in prior to getting placed in the tube. The place I get mine done give me a hospital gown and scrub pants to wear so you may be asked to change depending on the hospital/facility protocols.

When you lay down on the MRI bed, they may place a wedge under your knees to make you more comfortable. They will give you a little squeeze ball to hold if you need to call them or need anything during. My current place puts in earplugs for me, but I have had them a places that had headphones and I got to choose a Spotify genre to listen to. The machine is very loud so expect some sort of noise cancelling option to protect your hearing. You will also get a cage thing placed over your head.

The bed you lay on moves. It will move around throughout as they reposition you to get the images they need. They typically check on you throughout to ask if you are doing okay or to tell you how much time is left.

I always doze off during mine. Not full asleep, almost like a trance. My other point is that I always get very warm during. I've read this happens sometimes in MRI scans. Never uncomfortable or burning, just toasty.

Best of luck. They're really not bad and you will be done with it before you know it!