In the last few weeks I'm faced with a somehow strange behaviour of my Android device (Samsung Galaxy S4 Active, GT-I9295, Android 4.2.2, Kernel-Version 3.4.0-2015525):
If the phone crashes resulting in power-off when doing some CPU or network intensive task, it is not possible to boot it afterwards unless it is plugged into the power outlet. Even using a so called Battery Power pack as external power supply doesn't help.
In some cases, it boots until the PIN input. In other cases, it completely refuses to boot.