I had one previously long ago. Honestly, try not to be anxious. You may get an iv with contrast. The rest of the time, you are laying down. Just rest and shut your eyes. Let them know how you feel . They gave me ear plugs. Some people listen to music that they provide. It is really painless, I promise.
HI, I have never had one there, but I understand that they put your head in a type of brace to help keep it steady.
If you haven't had an MRI, be prepared to hear a lot of noise during it, sort of like being in a "Star Wars" movie, it is just the machine doing its work, it is actually fascinating on how it works, there are lots of sites about MRI's and how they work, you might want to look them up.
Most MRI's take about 30 minutes, they stop and go as the tech is setting it for different areas. The scariest part for me in when they move the table into the tube, so, I just close my eyes until that part is over, otherwise, I feel like my nose is going to scrape the top which it won't.
Try not worry too much about it, the techs are usually wonderful, they will go over any concerns you may have, and it will be over before you know it.
Hugs and blessings.