Dana,

I am unable to tolerate MRI'S unless I have some light sedation. Maybe if you have to have another then you could ask if they could give you something.
They might argue as it means you have to be observed by a nurse of doctor other than the MRI staff but they will do it rather than have you go without.
It is the intense noise that causes the vibrations--I liken it to lying beside a jackhammer
Lying in a "coffin" also worries me and my claustraphobia
Cheers
Tayla