docs: redirect loop warn (#1487)

* avoid infinite redirect

* chore: review

---------

Co-authored-by: Eduardo San Martin Morote <posva13@gmail.com>

docs/nuxt/auth.md

@@ -54,6 +54,24 @@ definePageMeta({
 </script>
 ```
 
+::: warning
+
+If you are using a [global middleware](https://nuxt.com/docs/getting-started/routing#route-middleware), make sure **you are not getting into a redirect loop** by ensuring `navigateTo()` is only called if the target location is not the same page:
+
+```ts{4}
+// middleware/auth.global.ts
+export default defineNuxtRouteMiddleware(async (to, from) => {
+  // ...
+  if (!user && to.path !== '/login') {
+    return navigateTo({ path: '/login' })
+  }
+})
+```
+
+:::
+
+````vue{2-4}
+
 You can even automatically handle the auth state by _watching_ the current user. We recommend you do this in either a layout or the `app.vue` component so the watcher is always active:
 
 ```vue