Will heartburn go away on its own?

Not always: depends on the cause. Look up lifestyle modification for heartburn. Also depends on how long you had it. Most commonly it is a mechanical problem and eventually you end up on medicine and if bad enough may seek surgical treatment ( if nothing else works)

Might: it might if you avoid eating before bed time and elevate the head of the bed 30 degree and avoid tomato and spices

Sometimes yes: Heartburn may be induced by several factors that can improve through lifestyle changes. Being overweight and smoking are two of them. If people lose weight and/or stop smoking, their heartburn often goes away.