What caused safe mode to come on

Solution
Most often it is caused by app or system errors. Sometimes an app or other software update gets installed that interferes with running the phone. Safe mode disables all third-party software, keeping only essential system processes running, to make it easier to troubleshoot issues and resolve errors caused by apps.
Most often it is caused by app or system errors. Sometimes an app or other software update gets installed that interferes with running the phone. Safe mode disables all third-party software, keeping only essential system processes running, to make it easier to troubleshoot issues and resolve errors caused by apps.
 
Solution