You can start by trying a restart on your phone. This will not erase any data and will not clear any settings that you have on your phone. To do this, press and release volume up, then volume down. After doing that, press and hold the power button. You may see the slider bar showing to turn off your phone. Do not slide this over, just continue to hold the power button. The phone will shut off, continue to hold the power button till you see the Apple Logo on the screen. At this point, you can release the power button and let the phone continue to boot. Once it has come back up, it has been restarted and you can check and see if that has corrected the issue that you are having.