The OnePlus smartphone comes with a touch protection against accidental touch, the so-called pocket mode.

Pocket mode prevents accidental touches to the screen or fingerprint scanner when the device is in your pocket, preventing accidental operation or starting functions and apps.

Android 10 | OxygenOS 10.0
Step 1:  Open the  Settings
Step 2:  Tap on  Utilities
Step 3:  Enable or disable  Pocket mode
  1. Open the Settings
  2. Tap on Utilities
  3. Enable or disable Pocket mode

OnePlus Instructions