Tell them apart by what they do

Six differences, and every one of them is about behaviour rather than content.

Where it comes from. A question is something you went and got. A symptom arrives uninvited, and it tends to arrive at prayer or at night.

How it feels. A question is interesting, sometimes uncomfortable. A symptom is alarming, urgent, and repellent to the person having it.

What you want. An answer, or relief.

What happens when you get a good answer. You are satisfied and you move on, or you get an hour and then the but what if arrives.

Whether it repeats. A question rarely returns in exactly the same form. A symptom returns in the same words, sometimes for years.

What you do about it. Read, ask, think, and stop. Or check, reassure, avoid, repeat, confess, ask again.