Is feeling remorse for not doing good out of fear of what people might say—such as prostrating in thanks to Allah publicly or calling people to good in the streets—considered showing off?

The blameworthy shyness (Al-Hayâ' Al-Madhmûm) in Islamic law is that which prevents one from performing acts of obedience (to Allah), guiding to good, enjoining what is right, and forbidding what is wrong. This type is not considered ostentation (riya'). However, prostrating in the middle of the street, specifically, is not commanded. As for raising one's voice when offering advice, it is permissible when there is a need for it, such as in teaching knowledge. It is blameworthy if it is without need or exceeds the required limit, based on the Almighty's saying: "And lower your voice; indeed, the most disagreeable of voices is the voice of donkeys."