My dad is 76 years old, he does not take any prescriptions. He has had vertigo for the past week. My mother said they were sitting at the kitchen table eating, and all of a sudden he starting falling forward. She caught him with her hand so his head would not hit the table and she said his body seemed limp. She shook him and then he opened his eyes and started eating again like nothing happened. He has never done this before. What could cause this, and what should we have him checked for???