Samsung Galaxy S4 GT I9505 Cyanogenmod 13 6.0.1 Marshmellow 'Andoid starting loop'

Please note that first boot always takes around 5 to 10 minutes to be sure that you've got boot loop on your device.

Before we go into the detailed instructions? Have you tried wiping dalvik cache? If not do it otherwise follow the steps below.

Here is how I would fix this issue:

1. Make sure that you've already installed USB drivers on the PC.


2. Also setup fastboot adb drivers. The minimal adb software by xda developer should work fine.


3. Hopefully you've got the ROM file, extract /unzip to get the boot.img file.


4. Copy it to the Fastboot drivers folder (Not needed if you've enabled site-wide adb commands, If you're not sure what I mean, I have written a guide on my blog)


5. Reboot your phone into custom recovery mode.


6. Run adb fastboot.


7. Type: "fastboot devices" make sure your device is listed.


8. Now type this command to flash the boot.img file:

fastboot flash boot boot.img

9. Once done reboot your phone using recovery options.

This method has worked for a number of people and devices including Motorola, Google Nexus, LG , Sony and HTC. Feel free to let me know if you have further questions.