What Could Be Causing My Seizures That Occur Before Or During Sleep Every 3-4 Years?

Hello Sir/madam I have a medical condition that is really bordering as i could not fine any cure or solution to it.I normally get seizures normally before i sleep or during sleep. It started when i was 17 years old since then its happens like every 3-4 years and when it happens i will get 2 episodes in two weeks the it will not occur again until after 3-4 years. I want to know what cause the seizure to happened and what are cures. Your assistant is highly appreciated. Thank you