My iPhone 6s is stuck on the white apple logo screen, it’s rebooting constantly. It is at the “Diagnostics” screen currently and I cannot seem to get this problem fixed. Is there a way to fix the phone without a laptop or computer?
iPhone 6s, iOS 13
I’m not sure what you mean by “diagnostics screen”, but if it’s requesting a connection to iTunes, you’ll need to connect to iTunes. Or transfer the device to somebody that can connect to iTunes, or to Apple or an authorized repair provider.
If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support
Restore your iPhone, iPad, or iPod to factory settings - Apple Support
More generally: If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support
iPhone 6s Stuck on white logo screen.
