Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with a doctor.
Without the ability to examine and obtain a history, I can not tell you what the exact cause of the symptoms are that your father is having. However I will try to provide you with some useful information.
I would have your father evaluated. There are several possibilities since the information is limited. One possibility is a seizure. Then, if it is a seizure, why? He may need neuroimaging as well as lab work performed. The other possibilities are movement disorders such as Parkinsons disease (to name just one). Is your father healthy otherwise or has any other past medical history? Many medications can cause tremors too.
I would recommend that your father be seen by a neurologist in the near future. If he has any loss of consciousness with the episodes, he’ll need to be evaluated more urgently like in an emergency department.
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.