What is the exact model of the laptop and if it is still under warranty I would suggest calling Dell tech support. With that being said have you tried a hard shutdown by pressing the power button for at least 4 seconds? If that does not help try a reset. Disconnect the battery and unplug the adapter. Then press and hold down the power button for 30 seconds. Then reconnect everything and try to boot again.

You haven't given us enough information. For example: 

• What model laptop (XPS 13 is a series, not a specific model)
• How is it frozen?
• Are you frozen on a screen image in a particular application?
• Is the screen black?
• What happened prior to the freeze?
• Does this happen often?
• What steps have you tried? (rebooting, power off, etc._

I can't know exactly what to suggest without knowing the situation. So, I will make guesses. Try these steps to see what helps:

• Press Ctrl Shift Esc to launch Task Manager. Select the frozen app and end its process.
• Press Ctrl Alt Delete to reboot.
• Press and hold Power button to shut down, and then reboot.

If none of that helps, do this:

1. Disconnect the AC adapter.
2. Disconnect the battery.
3. Press and hold the power button for 30 seconds to discharge any residual electricity.
4. Reconnect the AC adapter
5. Reboot the laptop.

The XPS 13 is a series and not a specific model. Your model number would be something like XPS 13 9350 , XPS 9310, etc. In the XPS 13 series the battery is in general removable but involves removing the back cover to do so. But if you are not comfortable opening up the system then a call to Dell tech support would be the next step.

Also the information posted by @filbert is spot on.  A little more information is needed to pinpoint the source of the problem.