I’ve definitely had this and I attribute it to nerves. I’ve never really been able to find anything about it either unfortunately, so I’m not 100% sure. I do know I have nerve damage in my left arm and will get that sensation of hot, prickling pain so when I get it other places I just sort of assume it’s a similar mechanism

Yep, that's "normal". I get it a lot when I have pain in that area. See if another person can feel it too (hot to touch). I've had it on my cheeks w/o pain too. It's just one of the many mysterious things that come with fibro.

Yes my chest area especially is a complete mess ;-;

Yes, it feels like I put my hands and feet in boiling hot water (I didn’t but it’s the best way to describe). I have nerve damage so that’s where that comes from. If I’m walking too long my back feels like it’s on fire and also my thighs feel like they are recovering from that but the burn is dull and it hurts to walk.

Yes! For me all my pain starts when I try to use my arms or legs mainly- but sometimes I get random pains too! It's a dull burning in my arms and legs that is painful but sadly and eventually you get used to it. If you can wear an should brace (or even wrapping gaze around) or something to hold whatever is having a fire fibro episode that helps- for me having pressure adds some relief temporarily and taking a nap (usually cause by then I'm too tired from the burning to do much else). Just don't keep the brace or gaze on too long