An MRI is a hell of an expensive diagnostic to jump straight to, especially if you don't have a specific area that is the cause. Most vets will recommend several cheaper things first.
I agree with going back to the vet (ask to see another one, maybe ask the receptionist which individual vet they would recommend for musculoskeletal things). I would assume your dog has hurt their neck, back, ribs, pelvis or something like that. Is it possible that they have had a slip or fall recently?
I would expect a vet to do a full body palpation/examination, see then walk/trot up, and maybe suggest a short course of a painkiller to see if that improves things, well before they suggested or agreed to an Xray (and then an MRI if needed).
I would also ask the vet for a recommendation for a canine veterinary physiotherapist. A bodyworker specialist will both be cheaper than an MRI and, working in conjunction with the vet and their diagnostics, could help find a physical reason for the pain. And I would assume this is pain related, unless there is a good reason to believe psychological.
Edited to be clear: I'm assuming neck or back since the vet has ruled out ears. The shivering is pain. Please don't ignore this.
One easy and inexpensive thing you can do is to treat him for ear mites to rule that out. Some worming/flea treatment tablets also cover ear mites, so this can be done with one pill rather than distress him by putting ear drops in.