Thanks everyone. I was worried it was her back legs and connected to the kidney disease, which was why I took her to the vets. But when she was wobbling around at home, it seemed like all four legs were shaking.
Drum is fine today - maybe a little quieter than usual but eating, drinking and having tummy rubs.
The vet examined her quite thoroughly - checked her eyes, limbs, spine, took her temperature and listened to her chest. She didn't take her blood pressure though, or do any tests. (Drum was fine at the surgery and even ate a Dreamie!) Couldn't find anything wrong and said to call over the weekend if the symptoms returned.
Drum had a whole bank of (eye-wateringly expensive) tests a couple of months ago which showed nothing apart from the signs of her CKD (which we've known about since last year).
There was a comedy moment though. My surname is George and this sometimes confuses vets. When the vet was looking at Drum's notes, this confusion kicked in and she said "Now, George is quite an elderly lady, isn't she?" I told her that I was getting on a bit, yes, but not yet elderly. My cat, however, was knocking on a bit.
She was
really apologetic.