Enter every time, is there a "Find Next" command in nano?
You can get a list of all keyboard shortcuts by pressing ^G (Ctrl + G).
From Main nano help text:
M-W (F16) Repeat last search
M-W is Vim/Emacs notation, where M means Meta (a key present on MIT and Sun keyboards).
On IBM-compatible keyboards – depending on, e.g., your window manager and terminal emulator – you can invoke the shortcut with Alt + W (hold, tap), Win + W (hold, tap) or Esc, W (tap, tap).
F16 can be emulated with Shift + F4 (hold, tap); in general, F<12+n> can be emulated with Shift + F<n>. In the unlikely case your keyboard has such a key, you can simply press F16.