Re: apps missing after restart Galaxy S5
Provided you are on stock and not rooted, it sounds like your device is extremely LOW on memory and is trying to preserve the OS. To start with, delete all call logs, texts, browser history, emails, pics (maybe share to the cloud) and uninstall any playstore apps that you don't absolutely need. After that do a reboot and see what happens. If they don't come back after that, you will need to do a factory reset.