Did her vet check her ears really well? My SM dog does the whole body shake a lot, every day, but it's her whole body not just her head like Laci. That's what made me think about her ears. Maybe she could have PSOM? Maybe in addition to SM? None of mine have ever had it so I don't really know what the symptoms are.
Both of my male dogs love to rub their heads on the carpets and both of them have been MRI'd and are SM free. That in itself is not worrisome to me. Oliver rubs his head against the sofa also. The yelping is the more worrisome symptom.