Indicates a person may feel nervous or anxious, often done subconsciously.

Sign of Anxiety

Can suggest boredom or impatience, watch for it in social situations.

Body Language

Others might find it distracting, try to be mindful of this habit.

Often implies trying to fix or understand something, may not be a serious attempt.

The person doesn't need to be an expert to 'fiddle with' something.

Not a formal way of fixing problems, more of a casual trial-and-error process.