My Samsung A5 2016 only turns on for a few seconds

It can only turn on while plugged into the charger, but it only turns on for a few seconds before shutting down. It can’t be turned on by pressing the power button, and while it’s plugged in it says that the battery is 100% charged but that wasn’t the actual percentage before this happened (34%). When I managed to turn it on and unlock my phone and removed the cable, the device just shutdown like when it reaches 0%. Is this a battery problem or something else? It’s been stuck like this for a few days and I need help!!