I personally think the most likely culprits are high VA (or volatile acidity ie. acetic acid), alcohol or SO2. Any of these can give a burning sensation... if the burning is in the throat, rather than on the tongue or in the nose, I would imagine it is VA caused by oxidation. I've tasted my fair share of homemade wines with high VA... even, or should I say, especially those made at ferment-on-premise shops that don't pay close enough attention to the wines. If you want to feel the burn, take a little sip of diluted white vinegar and you'll see how excess VA feels in the throat. It is usually also accompanied by some degree of off odors such as vinegar, or nail polish remover, but the intensity of these smells can vary quite a bit and can be masked somewhat by the wine's other aromas.