Screen activates after touch is turned off

Gravel bike vibrations mimic capacitive touch inputs and trigger the accelerometer/gyroscope. This wakes the display and registers phantom touches or accessibility shortcut commands (like volume or media control). To fix this, disable Raise to Wake, turn off Reachability, and use a fully enclosed secure pocket or top-tube bag instead of exposing the screen to handlebar vibrations

Try this

Disable Raise to Wake: Go to Settings > Display & Brightness and turn off Raise to Wake so physical motion stops waking the panel

Turn Off Reachability: Go to Settings > Accessibility > Touch and toggle off Reachability to prevent edge-swiping gestures from activating. 

Lock the Screen Manually: Press the side button to put the phone to sleep before placing it in your pocket or bag.

Use a Secure Storage Spot: Keep the phone deep inside a zippered jersey pocket or a padded frame bag where it cannot bounce against hard objects or catch wind/fabric friction on the glass.