Safe mode typically provides access to utility and diagnostic programs so a user can troubleshoot what is preventing the operating system from working normally. Safe mode is intended for maintenance, not functionality, and it provides minimal access to features.
Use hardware buttons to get out of Safe Mode:
If your computer is experiencing serious problems, either due to a software glitch or malware, and will not run properly, then you might need to use Safe Mode. Safe Mode is a basic diagnostic and troubleshooting mode that launches the operating system without most of its usual drivers and software.
Safe Mode is a feature on the Android Operating System used to solve problems with configuration or app incompatibilities. Restarting the device in this mode will load only the System's core applications. You can disable Safe Mode by encrypting your Android device.
Safe mode only disables third-party apps — you can still call people, send text messages, or surf the net on your phone's pre-installed software. More importantly, you can also uninstall programs and change your device's settings.
Safe Mode on an Android device blocks third-party apps from operating, and can help you diagnose issues with the device. Putting your Android in Safe Mode can increase its speed and fix errors, but limits what you can do with the device.
The reason why it's booting up in safe mode sometimes is because you're accidentally executing it's button combination when you turn on your phone! Below ate the instructions on how you enable or disable this mode when turning your phone on for your future reference.