By default, the Nest Guard (which acts as the main keypad for the Nest Secure security system) doubles as a motion sensor, and will sound the alarm if it detects motion. However, if you would rather just have it act as the keypad and nothing else, here’s how to disable the motion detection.
To do this, open up the Nest app and tap on the settings gear icon up in the top-right corner of the screen.
Select “Security” at the bottom.
Tap on your Nest Guard near the bottom. In my case, it’s named “Entryway”.
Select “Motion Detection”.
Tap on the toggle switch to turn it off.
At this point, your Nest Guard will simply act as the keypad and will no longer double as a motion sensor. Keep in mind that the keypad will still light up when it detects motion—so it’s not completely disabled—but it no longer has any say as far as the alarm goes.