Hi,
Maybe you have a problem with the volume buttons.
What do I mean, Android devices can be entered into Test mode by pressing a combination of hardware buttons, like Volume Down + Power or Volume Up + Power.
Maybe you have a liquid or other damage with the volume buttons, one of them seems pressed when you try to turn on the phone.
Try this, before switch on the phone, press the volume up and the volume down buttons stronger 2-3 times.
If the problem persist, the device needs repair service.
Regards.