Is my father having a seizure or a stroke?
This is a tricky situation. It is not uncommon for people to suffer from neurological "spells" after a stroke without a clear cut etiology. To a first order approximation, I would guess they are seizures since they come and go without leaving any permanent deficit and have been so stereotyped. In particular, these have the sound of "nocturnal seizures", in my opinion.
A typical evaluation for this type of problem would be a non-invasive angiogram (CT angiogram probably better than MR angiogram) to make sure there is no focal artery blockage that could be causing these attacks, along with a prolonged EEG (with part of the EEG done while he is sleeping). This may better identify the cause. If all else fails, I will sometimes start people on a gentle anti-seizure medicine to see if the problem goes away. If it does, you likely have your answer.
I hope that helps. Good luck!
