It's almost always when I'm hungry. And I'm not on a diet or something, or starving myself for days, else I wouldn't ask this question. As far as I noticed the 3 factors that affect it the most are:
-not getting atleast 6 hours of sleep
-not going to the toilet as soon as you have to defecate
-skipping a meal
All of this combined is usually the worst, but skipping a meal is the biggest factor.
But this happens if I skip just one meal. For example, if I had a good breakfast in the morning, but skipped 3pm launch, by 6-7pm I would be experiencing a mild fever. My temperature would raise (not that much like when I am sick but still higher than usual.) and I would be weak physically like I am about to faint (although that never happened).
Also, I don't know if it matters but I must say that I am working out in a gym last 3 months, but this started happening maybe a year ago (the same time my appetite suddenly increased and I started gaining weight, which is good since I was really skinny for my height. I am 1.95m tall and have 93kgs currently (was atleast 80))
This "fever" (if it is fever at all) usually passes as soon as I eat something, but last two times lasted even after that (maybe 15 minutes) so that is a reason why I'm writing this.
p.s -about a nickname: No, I'm not doing any drugs or did them in the past (or use any weight gain supplements for my gym, the increased appetite just popped out of nowhere) it's just a name of a song. I have no reason to lie since this is annonymous. I also don't smoke, but do drink, usually only during weekends. I had a sort of history of losing conciousness when I was young (epilepsy, but a mild one) but that was caused by a sudden pain shock, or staying too long in the hot sun. But it hasn't happened in like 10 years, because it was treated.