Welcome to the Community,
Is the system freezing up and you are not able to use the system(including your mouse cursor)? I suggest you to turn off system using the power button.Release flea power.Disconnect the AC adapter,remove battery,press and hold down power button for 30 seconds.Reconnect battery and charger and turn on system normally.
If this is happening frequently,check if system is overheating.Check if the fan is running normally.Also run the Dell 32 bit Hardware diagnostics and post back error code/message if any.
Use the link below to run the Dell 32 bit diagnostics: