Hi,
This is a fairly common problem with LG smartphones. Unfortunately, it can only be solved by hard resetting the device, and deleting all the user data. The LG smartphone bootloop issue is most commonly caused by malware and/or partial corruption of the user data partition. To learn how to hard reset your LG Stylo, please refer to this guide: https://www.hardreset.info/devices/lg/lg-stylo-2-ls775/hardreset/first-method/