iPhone SE powers on whenever moved, defective?

Got a new grey iPhone SE for Christmas from the Verizon store. Seems to work fine except for one issue. When the phone is off (standby), any sudden motion turns the phone on, as if the home or power button were pressed. Let me be clear: Nothing is in contact with the power button or home button when this happens. The phone isn't getting any calls or messages or other notifications. There's a passcode, so nothing bad happens, but it's unsettling to open the pocketbook and see the phone screen all lit up. Is this something deliberate? Can it be configured? Or is the phone just defective?