You might get checked for Chronic Active Epstein Barr Virus. I was having the same symptoms, multiple times a year. I couldn't believe how often I was getting "sick", and the fatigue was horrible. I was diagnosed in 2017 and unfortunately, there is no cure. I have learned to "manage" it with l-lysine and monolaurin. CAEBV is one of the top viruses thought to cause MS. *I'm not a Dr. 😉

Yes I have flu symptoms sometimes only last for a day, it's strange.

Yep, I attribute it to exhaustion,happens any time I am over active or just try to do a "normal" days labour.

I have not received either Vax. My last infusion was Lemtrada 4 1/2 years ago. I definitely do not have covid or the flu.

That's a huge question there are many reasons possible. Have you had covid or flu vaccinations? Ms usually doesn't cause this so it is likely independent of ms. Do you take one of the daily injections? Such as copaxone, or had an infusion? If not, again likely and independent situation.