iPhone 7 randomly shuts off by its own (plugged or not)

My iPhone 7 has been randomly shutting off lately ( while charging or not) , I put my phone in the charger and left it for around 3 hours (I was out of the house) then I came back and it was off, it wouldn't start at all, I tried plugging it in the charge again but it didn't show anything then I tried holding the power button and the volume down button and the apple logo appeared and the iPhone opened again. it kept shutting off by itself and I tried to hard reset it, I updated it to latest version of IOS, I checked the battery health ( currently supporting normal peek performance) but the issue still persists, every time it shuts by its own I would have to hold the power button and the volume down button again and again . how do I fix this please.