Phone got blazingly hot and started to act glitchy
Same thing happens to me. Normally all phones heat up  there are some which are a bit pro at that. if u keep a phone of that sort under pillow (cloth). There wont be a method for heat to escape. So it will continue getting hotter. The reason for battery drain is cos the energy stored in the battery is being released as heat. So don't keep phone under the pillow or anything of that sort to avoid it.
Hope this helps :)