have you updated your device to the latest public build? check under settings>system>about current OS build is 14393.321. check under phone updates if you have any pending updates as well. As you have a new device in hand i believe there will be a couple of major updates to be installed.
In case you are on the latest build perform a soft reset by holding together volume down+power key until phone reboots, and check if that resolves this issue. *If the issue remains , you will have to perform a hard reset and start fresh without restoring a backup.
+I should make you aware of the fact that since the inaugural of windows 10 mobile Microsoft has suggested not to restore a backup and to start afresh after updating to windows 10 mobile. This was done to prevent any kind of bug or glitch to appear.
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