The same problem was with my Murano. Asked bodyshop, they told brake disks needed to be replaced. I did not want to replace them. When I was replacing front brake pads by my self, I noticed that caliper bolts were completly dry from the factory, so lubricated them, installed new brakes and now my Murano rides quite and no wheel shaking when I slowing down. If you do not need new brake pads just lubricate caliper bolts and shims, it's easy to do by your self.
Ever since I bought my Murano it needed new tires. Initially assumed (after the dealership who promised to replace them then refused) it was due to the tires. Bought new tires from Discount Tires. Still shakes. Take it in constantly and they say it's out of balance each time and this his been constant. Now, of course, that my tread is down to where you should replace your tires, selling me a new set is the "sing-song" to fixing my problem.... Quite frankly, didn't fix it last time.... think it's one of those mystery Murano issues that is unfixable.... all cars seem to have one or another :(. Just don't make things like they use to.
So this is NOT a vibration on braking yes? Because that is a brake system issue. I have found that many OEM tires are poor quality, remember the Ford Explorer tires exploding with the original factory tires? I go the distance when I buy tires, I buy Michelin Harmony, (NOT COSTCO as they are not real Michelin, they will NOT be warrantied by any Michelin dealer, only COSTCO will work on them) They are pretty expensive, but they balance perfectly, so no shimmy. Remember tires are a critical safety issue, that is why the Dept of Transportation made tire pressure monitoring systems mandatory. At least 25% of the vehicles on the road are being driven with defective or under pressured or worn out and unsafe tires that take thousands of lives each year in the US alone.