The server crashes periodically, so please save your work before closing any files.

伺服器不定期會當機，所以關閉檔案前請先存檔。

Our sales manager periodically drops by the warehouse to check on shipping progress.

我們的業務經理偶爾會到倉庫看看出貨進度。

Customers periodically call to complain about delays, though there is no clear pattern.

客戶偶爾會打電話抱怨延誤，不過看不出有什麼規律。