iPhone 16 Pro Max keeps switching to camera automatically

Not much to build an answer around.

Is the Camera app unexpectedly active when picked up, always, randomly?

As a guess: Turn off Tap to Wake, and try again. Settings > Accessibility > Touch > [setting]

Maybe the Camera app is set for back tap? Settings > Accessibility > Touch > Back Tap > [setting]

And one more idea. The iPhone 16 lineup introduced a new button located on the bottom right side of your iPhone, called the Camera Control, which when pressed will open the camera. It can accidentally be pressed if you're holding your iPhone firmly. If this is a bother to you, you can change the setting in Settings > Camera > Camera Control. First try a double-click, and if that still doesn't help you, you can turn it off entirely.

There’s also the Action Button on iPhone 16 Pro Max, which can be set to open the camera.

Settings > Action Button

More great thinking!

You might be accidentally hitting the camera button? You can turn the button off in settings if you don’t use it.