Sublime Text 3 highlights all instances of currently selected text. Is there any shortcut to navigate cursor to the next / previous instance (copy) of selected text?
Yes, all you need to do is edit your key bindings (Sublime Text -> Preferences -> Key Bindings User) for "find_under". Copy & paste this into your bindings and set your keys (defaults are "alt+super+g" and shift+alt+super+g)
{ "keys": ["alt+super+g"], "command": "find_under" },
{ "keys": ["shift+alt+super+g"], "command": "find_under_prev" },