Basic Android Samsung Galaxy 4 on ATT No special launchers Not rooted. Just a normal out of the box Samsung 4. Somehow I have moved the 'app dock' to the middle of the screen. Tried long pressing the 'apps' button to drag it back to the bottom, but you cannot long press the apps button. Tried long pressing the other buttons and it looks like I'm able to drag them to the dock at the bottom, but when I release, they snap back to where they were to start.
Here is a nice tutorial for rebooting Samsung phones in Safe mode. It should solve your problem.
Booting Samsung Galaxy S4 in Safe mode.
Note - In Layman’s language, if you’re facing any issue with your Android mobile and need to troubleshoot and check which applications might be causing an issue, then you can boot into safe mode, this means your device OS will load without any third-party apps.