During a generalised seizure a dog may fall over, become stiff, make paddling movements and lose consciousness. Afterwards a period of confusion, restlessness or tiredness is common. Not every dramatic-looking episode is an epileptic seizure, however, so a video can be very valuable if it can be filmed from a safe distance.
The cause may be in the brain, but seizures can also be triggered by certain poisonings or metabolic disturbances, for example. After a first seizure, the vet assesses your dog's age, medical history and neurological status and decides which tests or examinations are needed.
Move furniture and objects your dog could hurt itself on, but do not hold it down and do not put anything in its mouth. Time the seizure. Seek emergency care if it goes on for a long time, if several seizures come close together or if your dog does not recover normally between them.