Settings option screen all white

Force-close the Settings app: Open it, swipe up to go back to the Home screen, then swipe half-way up and pause to open the App Switcher screen. Swipe the Settings app up and off the screen. Then try opening Settings again. If it still doesn’t appear to be normal force-restart your iPhone:

• Press and quickly release VOLUME UP

     then

• Press and quickly release VOLUME DOWN

     then

• Hold the SIDE button until an Apple logo appears (15-30 seconds), ignoring "slide to power off" if it appears

The operative word here is QUICKLY; and try it a couple of times, the timing is a little tricky. If done correctly this will always work unless the phone has a hardware problem.