Is a deep sigh while listening to the Holy Quran or a religious sermon considered a sign of distress and an offense to Islam, or disbelief?

Whoever has established certainty in their faith, it does not disappear except by a similar certainty. Doubts and whispers have no اعتبار (validity) and are from the wiles of Satan; they must be repelled. Allah does not hold His servants accountable for mere self-talk (حديث النفس). If the heart is open to faith and fears disbelief, this is a sign of goodness. There is no accountability for what crosses the mind by way of self-talk. If one is afflicted with obsessive whispers (وسواس), they should ask Allah for healing and be diligent in seeking lawful Ruqyah (definition) (Islamic exorcism).