How to disable proximity sensor check? Phone restarts every 5mins

To the best of anyone's knowledge outside of Apple, there is no way to disable the three minute sensor scan. As such, if you want your phone to be usable, you will have to replace the damaged component or repair the flex cable.

You say you don't need the proximity sensor, but it affects how you make and receive phone calls. Its major function is to turn off the screen and disable the touch screen when you hold the phone up against your face; without the proximity sensor, you'll be making random touches on the screen with your face, resulting in who knows what function. So unless you plan on making all your phone calls on speaker, it's advisable to replace the sensor.

Naturally Apple is making this process as difficult as possible. Aftermarket repair parts are readily available both here at iFixit and elsewhere, but you will lose Face ID if you use them. If you are updated to iOS 18 or later, you can use the Repair Assistant to pair a new or used genuine Apple front sensor assembly to your phone and get back the Face ID functions. Note that if it's a used part, the phone it came from cannot have been reported lost or stolen.

So your choices are to use an inexpensive aftermarket part and live without Face ID, or buy a new or used genuine Apple part and get your phone fully functional again. Either way the three minute boot loop will stop and you'll be able to use your phone again.