From what you describe it sounds like your dog had seizures. My last Giant Schnauzer had them frequently. She lived a happy healthy life despite having epilepsy. It's definitly a good idea to take your dog to the vet. He/she will probably suggest a blood test. In most cases the cause of the seizures is never found. Here are some links to help answer some of your questions...
www.canine-epilepsy.net/basics/basics-index.html

www.canine-epilepsy-guardian-angels.com/seizures_overview.htm

Stacey &
Zoey ( Giant Schnauzer )