Summary:
I had a feeling of irritation/inflammation/dryness, and certain weeks I had an unbearable burning sensation, as if my saliva was burning me. It turned out that I slowly developed a habit of pressing my tongue against my palate or front teeth, and after I tried relaxing my mouth and tongue, I felt tingling and realized that my mouth was numb, especially the tongue and palate. I also massaged the jaw muscles and stretched them by opening my mouth. The burning quickly went away (maybe a few hours to completely go away). As for the sensation of irritation and the tongue feeling weird, that is because of the numbness, and it takes a few weeks to go back to normal. Just don't forget to relax the tongue and mouth, until it gets natural again.

Details:
I may have had the same thing as you @willows, and I had no idea my palate was numb. I was feeling that my mouth was irritated/inflamed, and certain weeks I had an unbearable burning sensation and couldn't sleep or work. I went to the emergency at night once, I thought it was an infection, but no one was able to help. This lasted more than 6 months, I've seen almost 10 doctors and specialists, and some gave me a lot of Miconazole, Fluconazole, ..., thinking it may be Candidiasis, even though my mouth looked normal.
Since no one could help me, I started doing a lot more research. I thought that it was my saliva burning my mouth because when I tried sugarless candies or chocolate, it got worse. I bought some PH paper tests to see if my saliva had an abnormal PH, but the PH was normal. On the Mayoclinic page about Burning Mouth Syndrome, I saw that one of the causes can be tongue thrusting. I almost ignored it, but then I thought maybe I'm doing it unconsciously, so I tried to relax my tongue and jaw, and that is when I realized that my tongue muscle was contracted! I started to feel tingling especially in the tip of my tongue, and the burning sensation stopped! Then I realized that my tongue and palate were numb, I had no idea before that.
I still had the irritation/inflamed feeling, but then I realized it's probably an illusion that the numbness tends to give us, or the poor blood circulation could have inflamed the areas too. So now it's been 2 weeks and the numbness is almost gone, and I'm completely healed and can live normally again.
The reason candies and chocolate, and acidic drinks were making the burning sensation worse, is because we use our tongue and mouth muscles even more to suck on the chocolate and candies. And acidic drinks tend to make our muscles contract, like lemon does.
Funny note: during my research I went on a gaming channel, a place where there was 20k random people, and I asked if anyone had a similar experience. Someone told me that he found out he was biting his cheeks during sleep. This is not the same as me, but when I read "Tongue thrusting" on Mayoclinic, I might have ignored it if it was not for that person's similar experience.

I think that the other causes of "secondary burning mouth syndrome" on Mayoclinic, like stress, anxiety, dry mouth, are just indirect causes. For example, stress or dry mouth tend to make us close our mouth and contract our muscles, but it could be that the real reason is the tongue and mouth muscles being contracted and preventing good blood circulation.