If your Samsung Galaxy S4 on Verizon has been randomly rebooting, you might want to check for a system update. No, it's not getting Lollipop, but Verizon says that this update does fix "the intermittent power cycle issue." Translation: before this update the phone crashed. Now it will not crash. We hope. The only other change for software version KOT49H.I545VRUFNK1 (PDF link) is a VPN connectivity fix.
Verizon's S4 has gotten a few of these small updates, so you should know how it goes by now: any modification to the system or the recovery will cause a flash error, and if you have root before the update it's possible you might lose it afterward.