Welcome to Nokia Support Discussions! Here you can share advice and tips with thousands of other Nokia users around the world in English. Many Nokia employees also follow and participate in the discussions, see our guidelines for more information. Everyone can search and read the discussions, but to post your own question or reply to others, simply sign in with your Nokia account. If this is your first time here, you can choose an alias to represent you. And if you don't have a Nokia account yet, please register.
have you checked via Nokia Suite if there are any firmware updates available for your device? IF there are, please update to the latest version offered. Failing this, try re-installing your current firmware, and if this doesn't work either, then you can try performing a three-finger hard reset. Please remember to backup all personal data on your PC or online storage equivalent.
Failing all of that, you will need to take your phone to your local Nokia Care point for them to inspect: http://nokia.com/support