Does anyone have periodic fever episodes that last less than 12 hours?

For the past 3 years, I have had unexplained fever spikes that last a short period of time. Usually less than 12 hours. They always start between 4 and 6 A.M. I have body rigors and temperature that spikes sometimes as high as 102.5. I generally take 2 tylenol and go back to bed and fall asleep for a couple hours. When I wake up, my temperature is usually less than 100 degrees, but not down to normal. Lasting effects are sore muscles from the excessive shivering from the rigors. But that's it.

I can generally go about my normal business once my temp falls below 100. Other than that, I have no other symptoms.

I have had extensive blood work ups and everything is normal. My gall bladder was removed but no difference. No doctors can seem to find a cause. I suspect it may somewhat related to times of elevated stress, but not always. Food and drink don't affect when it happens. In the beginning I was having them once a month, and a couple months, twice a month. Lately, it's been a few months between episodes.

Trying to find others who may have these fever episodes. I feel so alone. And the fact the doctors can't seem to find anything, doesn't help.

Any insight is appreciated. Thank you.