The most common cause of coughs are upper respiratory infections (colds). These are usually obvious with other symptoms including not feeling well. However, all coughs are not from infections. Here some things that may be the cause of your cough:
Not everyone with asthma has the classic wheezing. Some people have coughing from uncontrolled asthma. This can be especially bad at night.
This especially true, if you have seasonal allergies and suffer from postnasal drainage.
People who have heartburn with certain foods may notice a worse cause. This is usually worse with laying flat.
Blood pressure medications (ACE inhibitors) like lisinopril and captopril can cause a cough. This resolves with stopping the medication.
There are many other things that can cause a cough. If you are experiencing a prolonged cough you should see your doctor for evaluation.