Why does my iPhone restart itself after 3 minutes when using an app?

About a week ago, my iPhone SE stopped recognizing when it was plugged into a charging cable while I was in Kuwait (the charger was plugged into a UK-US adapter). The phone would only charge when it was off. The next morning, it began to restart itself every three minutes if any application was in use (to include an alarm clock). If not apps were in use, it would not restart. Since I was traveling, I did not really do much with the phone until three days later, when after sitting off for a day or two, the phone began to work like normal. I quickly backed up the phone. The phone then worked fine for another two days even while being charged. However, it then no longer recognized the charging cable and has since re-entered the restart cycle of three minutes when an app is in use. I did manage to reset the phone last night but it will restart three minutes into the restore phase. I suspect that my battery has gone bad but am not in a location for the next few months where I can get it repaired or have the parts sent to me to replace the battery. Are there any other potential causes I may be overlooking?