S6 edge plus wouldn't turn on or charge

[AC Question]

Last night my husband plugged in his s6 edge plus before going to bed. Everything was working as it should. He woke up this morning and his phone was off, it wouldn't turn on and it wouldn't charge (the charging light wouldn't come, nothing.) Like it was completely dead. I tried holding down the power button, nothing. Holding the power and home, nothing happened. Then tried holding the power, volume and home to reset like the techs told me to, and nothing happened. It had no sign of life. Then 2 hours later the phone turned on and everything works like it should. Has anyone had this issue, and the phone continue to work fine, or is this going to be an ongoing issue? We're going to back everything up just in case, but wondering if he should just get a new phone instead. We bought it used, although it is under a year old, Samsung won't do anything for him.