my iPhone XS Max has frozen

If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support

"If your screen is black or frozen

If your screen is black or frozen, you might need to force restart your device. A force restart won't erase the content on your device. You can force restart your device even if the screen is black or the buttons aren't responding. Follow these steps:

• iPad models with Face ID: Press and quickly release the Volume Up button. Press and quickly release the Volume Down button. Then press and hold the Power button until the device restarts.
• iPhone 8 or later: Press and quickly release the Volume Up button. Press and quickly release the Volume Down button. Then press and hold the Side button until you see the Apple logo.
• iPhone 7, iPhone 7 Plus, and iPod touch (7th generation): Press and hold both the Top (or Side) button and the Volume Down buttons until you see the Apple logo.
• iPad with Home button, iPhone 6s or earlier, and iPod touch (6th generation) or earlier: Press and hold both the Home and the Top (or Side) buttons until you see the Apple logo."

-AJ