Q: Blue Screen, Auto Reboot

Hi,

I'm having this auto reboot with my iPhone 6 iOS 8.1.2 it happened twice during a week time today I've seen the second time with a blue screen for a second only before auto reboot, first time I was using Viber, the second time I was using Safari only! I've updated to this version of iOS since it was launched, I didn't notice this till last Saturday. Any ideas?

I've been using an iPhone for the last 4 years, this is the first time I see something like that.