My Teddy suddenly had a seizure, trembling and unable to stand, with changed pupils, then recovered after a short while. This also happened two months ago.

Take a seizing dog to the vet promptly. Epilepsy, neurological disease and brain parasite infection can all cause this. Repeated seizures are likely epilepsy; record a video next time with the timing and symptoms to help diagnosis.

Clinically epilepsy shows fixed staring, rhythmic jaw trembling, spasms, loss of consciousness, violent limb thrashing, foaming and incontinence. After diagnosis the dog needs regular anti-epileptic medication and a calm environment free from fright.