Yes, I have had this, or actually, I have this. For me, it started as a result of concentration, and then I used it as an object of concentration, and then it took off by itself in a Kundalini-type way. For a while, it got intense. It was too much. I would have to cool my chest with a damp cloth and/or walk outside in the winter with my coat and shirt open. It wasn't just psychological either. Other people could feel it with their hands. It was genuinely hot. It was quite freaky.

Over a few months, it calmed down and I learned to modulate it. It's mostly around my heart or in my belly, but I can spread it around further if I want. It's not a problem. In fact, it's a nice upgrade. It's a reminder that comes on its own while I am meditating or just while I am lying in bed or sitting around. It's kind of like ET's chest glowing when friends are near. This sounds hokey, but it also tends to show up after significant insights. I can also turn it on at will. I have used it for mundane things like warming up on a ski lift or when caught in the rain. I actually have the warm glow in my chest as I write this, because I'm thinking about it. But after those first few months, it never reached uncomfortable levels, or was anything other than pleasant. 

I looked into it and it seems most likely that it is brown fat being activated by neurotransmitters. It happens in daily life when people are in very emotional situations, which is why we have expressions like "warms my heart" and "hearts glowing with pride." For most people it's rare, but it seems that mediation practices can activate the system responsible, either temporarily or semi-permanently. I've had it for five years now. 

My advice, which may be wrong for you, because I'm only basing it on my own experience and a little internet research, is not to worry about it. If you pay a lot of attention to it, it does tend to grow. If it gets distracting, maybe go for a walk. I guess I would suggest thinking about it like a pet. But don't try to teach it any tricks, or at least not until you are really comfortable with it. It's important to treat "energy systems" with respect. I don't really believe in "energy systems" but I still treat them with respect. I have heard reports of people having considerable difficulties with related things, but never with heat. Still, respect. 

I think that, for many people, it's temporary, so don't get attached to it either. 

Had something similar years ago, caused by essentially accidental tummo practise, and later fire kasina. Something I found useful was to use visualization to bring it back the other way. Get concentrated and then imagine yourself sitting on a block of ice in the arctic. Not uncomfortable, just cool. Imagine the coolness flowing through you just like you did with the warmth. Third jhana can also have a nice cooling feeling, like you're submerged in a calm and cool lake. As a side note, it can be interesting to notice during this sort of practise that cold and heat are very similar from a sensation perspective. What's the difference?

Like Martin mentioned, it's temporary. It also can't really hurt you, so just notice whatever sensations arise and treat it like any other obstacle in meditation. Hope this helps.

Yes, this sounds like the spiritual heat generated during Tummo practice. It is not a bad thing, Tibetan's and Martin use it to warm up in the cold. It is Kundalini and there are secret Tibetan practices that will allow you to control/direct this spiritual heat. I recommend discussing this with a teacher qualified to teach Tummo. My teacher is Peter McEwin, and I recommend him. Have you tried meditating in the cold, might be a fun experience for you.

I am a Tummo newby. I'm not qualified to give you in depth answers, but can tell you my experience. I have had no issues with the tummo practice in warm weather, as the heat generation has only come up when it's been needed. It has never come up on its own and when I am done with meditation it sticks around briefly, like how you'd generate heat from a long run in the cold. I can not generate heat at every session, but the longer the meditation session and the colder it is, the more warmth I've felt. Tummo is not just for heat generation, it is a completion practice and can lead you to awakening. A component of the practice is working with the prana and kundalini, and dispelling problems that can develop with both. People that are having issues with uncontrolled kundalini, should benefit from this practice, and this is why I recommended it to you.

Yes happened to me at the beginning with fire kasina. I eventually turned to the jhana ladder for my shamatha base and then now to shikentaza. Equinamity is a good skill to learn for these in my opinion.

​​​​​​​I probably should also say I tried other means like grounding to earth, black tourmaline, water kasina but none of those methods worked for me as well as internal energy transmutation. Eventually you will probably need the same skills for other things anyway.

Yeah, heat/fire/elemental imbalances are a thing, definitely, as noted in lots of good advice above. Focusing on space, water, earth, feet, images of cold, etc. all good, as has been mentioned. Cool or luke-warm baths and showers helpful sometimes. 

Good luck! 

D