Your toothbrush may come with different modes and settings. Once a mode is selected, the toothbrush works for a specific time period and then turns off automatically.
Here is an overview of possible modes and their timings:

Clean = 2 minutes
White = 2:30 minutes
Polish = 1 minutes
Gum care = 3 minutes
Sensitive = 2 minutes
Gum health = 3:20 minutes
Tongue care = 20 seconds


 

Does the vibration of your toothbrush change momentarily while brushing, but still continues to vibrate? If yes, this means the time pacer or the pressure sensor is on.  
These features indicate when you are supposed to move onto the next section of your teeth via a brief change in vibration. These changes are normal. The toothbrush will automatically turn off at the end of the brushing session.
 

If your toothbrush turns off before a brushing cycle is completed, there could be a malfunction in your device. In this case please contact us for a repair or exchange.