Why has my Nokia Lumia 625 frozen?

[Windows Central Question]

my nokialumia 625 has froze it wont work or switch off

iwas taking a video but was interupted so swithhrd off but screen just went blank

 

[Abhishek P]

Re: my nokialumia 625 has froze it wont work or switch off

Keep pressing the volume down and lock buttons together for 15 seconds, the phone will reboot