Why is my Samsung s5 phone not switching on?

[Android Central Question]

I was on phone at it randomly switched off in my hand, its only 3 months old and has no cracks on the glass or inside the glass, I have tried charging it for hours and no red light shows up, the battery is charged because i put the battery in another s5 and it switched on, I have tried holding the power on button multiple times and it just in reacting or vibrating... does anyone know what happened??