If you experience a reboot loop, force restart the device (Hold Power + Home).
If you want to jailbreak iOS 9.3.5 today, you will use one of two highly reputable, community-tested tools. Both are semi-tethered. 1. Phœnix Jailbreak (32-Bit Devices) ios 9.3.5 untethered jailbreak
Go to the tab and look for the appropriate untether package for your tool (such as Community Offsets or the specific Untether package recommended by your chosen jailbreak utility). If you experience a reboot loop, force restart