Here you can find information on some customer symptoms connected to the centre display and how to perform a restart.
The video only applicable to models with Google built-in.
Some general issues with the Centre display - like connectivity problems can be solved with a restart.
To restart the Centre display, press and hold the home button below the Centre display for 20 seconds. This leads to the screen cleaning mode. Continue to hold down the home button and the display will turn off and then restart with the Volvo logo. You may continue to use and drive the car as normal after this step.