Hard resetting an iPhone 12 can often help if it's unresponsive or having issues. To do this, quickly press and release the Volume Up button, then the Volume Down button. After this, press and hold the Side button until you see the Apple logo. It should restart your device. Have you been experiencing frequent issues with your iPhone lately, or is this a one-time situation? If you'd like, I can offer more tips to keep your device running smoothly!