Coincidentally Stanley our 8 year old greyhound started having seizures in October last year. We have only witnessed 4 of them but of course he could have had more. He basically looks drunk, eyes stare, he shakes slightly, his heart races, he looks scared, tail goes between the legs and he can't stand straight and they last for 2 mins. We took him to the vet and she just told us next time to see if his gums go pale which would indicate the heart or if his eyes flicker from side to side, it would be the brain (or something like that). She wasn't too concerned and we haven't run any blood tests as that is not common practice in NZ, but of course we can opt to if we want. She did do a fairly thorough examination (without the bloods) and everything seems normal for him. She also said to try and film it on phone or camera if we can so she knows what it looks like.
Pretty scary the first time he had one but we are used to it a bit now, although you always hope it isn't anything sinister.
My black lab growing up had the most awful epileptic seizure when he was 13 and was put down not long afterwards, however that was over 30 years ago.