I managed one time to start a fire by just boiling water. I had this kind of immersion boilers.
Switched it on in my room and then forgot it while talking with other guys in student accommodation. I remembered, only when I saw smoke coming from my room. Water was completely evaporated, the wire of the boiler started to burn and the already small flame on table and on wall by that table was running high. I managed to extinguish the fire with the thick blanket that was there. So it all ended well except a lot of stress and my room needed complete renovation.