Strange Symptons-I am writing on behalf of my f

Maybe pancreatitis? I am writing on behalf of my father. He is 73 years old and in excellent mental and physical health. About twice a year he comes down with these strange symptoms that put him in bed for at least 4-5 days. There is no rhyme or reason for them and I was hoping that someone could help. Usually, the first day he starts to feel dizzy and very tired (almost cold-like symptoms)his head gets cloudy and he gets very disoriented. Then on the second day he is so tired that he cannot get out of bed. His mind is running miles a minute and every time he closes his eyes, his eyes twitch and he cannot relax. He cannot sleep for about 24 hours. He gets chills so bad that he cannot control them and bundles with 4-5 blankets, then the chills turn to hot flashes. The next day he cannot move, pure exhaustion. He is pale and has no appetite. He is so weak that it hurts him to breathe or talk. This contuinues for a few days then he starts to feel slightly better and by the 6th day it is gone like it never happened. This experience follows the exact sequence every time. It used to happen once a year but now it happens twice a year. This has been going on for 30 years. Other than this, he never gets sick and is in perfect health? Does anyone have any ideas, please? ||| Maybe pancreatitis? ||| Just a thought, could it be malaria?

Symptoms of malaria include fever, chills, headache, muscle aches, and malaise. Early stages of malaria may resemble the onset of the flu. Travelers who become ill with a fever during or after travel in a malarious area should seek prompt medical attention and should inform their physician of their recent travel history.