triangle on startup

[zzcool]

i left my phone then i came back to it being just black i couldn't turn the screen on so i assumed the battery had died (turns out it was at 82%) i connected the charger and the notificationlight started blinking twice blue or something, i managed to turn the phone on and it showed a triangle with a wrench inside for like 2 seconds then it died again and restarted then it started normally and asked me to update it, what actually happened?

the update wen't fine afterwards no issues what so ever.

[Uliwooly]

@ZZCOOL

That's quite odd, but if it only happened once you shouldn't worry about it.

[zzcool]

i don't since it works fine now, but it's somewhat of a worry that it even happened  or why it happened it was just random.

[Jeffrey04]

I also get that triangle sometimes after rebooting due to problems (mainly bluetooth and wifi since march update). But then after that the phone would boot normally, not sure what happens. Some sort of system repair/recovery taking place?

[Kristen40]

Happens to me quite often as well when I reboot my phone no idea why as it only started happening the last couple of months  

[Amir58]

i have same problem and my phone is not working, the screen is black while phone is on and also PC could not detect the phone.

any bodye faced with same problem?