There is a Terminal command that you can use to quickly make your dock look like new again. Do you experience problems with the Dock on your Mac? The best you can do is to reset it to default settings.
The following Terminal command will reset your dock by removing any icons that you’ve added and removed. It’ll also reset the size of the dock, magnification settings, and its location.
Resetting the Dock to factory settings
Copy and paste the following command in OS X/macOS Terminal:
defaults delete com.apple.dock; killall Dock
Hit the enter key and the Dock will quit and relaunch itself into the default settings. Of course you can rearrange and adjust it again.