Phoebe, an Italian Greyhound I had, had this type of seizure every 6-8 weeks or so. Her legs would splay out, her body and head would wobble from side to side, and she'd tremble. You could tell she was aware she'd lost control of her body, but she couldn't do anything but ride it out. I'd hold her when she had them, because occasionally she'd stagger-run while seizing and crash into walls.
The only trigger I ever identified was overheating, as they did seem to happen most often when she had been sleeping under covers for a long period of time, though they happened at other times, as well. I adopted Phoebe when she was 6 years old, but her first seizure happened about 2 years earlier.
When I made the switch from kibble to prey model raw feeding, her seizures reduced dramatically. She went from seizing once every 6-8 weeks to once in 2 years.