How to start in Safe Mode iPhone 6
The Safe Mode is designed to turn the iPhone with the minimum possible resources. When you start in Safe Mode iPhone the first thing you will notice is that you no Tweak works, all are disabled, so you will not have any problems.
To launch the iPhone in Security Mode (Safe Mode) simply you have to give the power button and immediately after you press the volume up button and hold it until your iPhone starts.
With this simple action will get boot your iPhone, because only the essentials load.
Now go to Cydia and begins to uninstall the tweaks that you think give problems. If you are unsure of which can be, you begin to uninstall in the reverse order that you place them, that is, from last to first.
When you finish off your iPhone and turn it on, but now as usual, everything will return to normal if you've removed the Tweak bothered. If not, repeat the process until everything works properly.