When it comes to describing the act of feeling sudden inspiration or motivation, there are various synonyms that can be used in place of the phrase "when the spirit moves". One possible synonym is "when inspiration strikes", which conveys the idea of being suddenly seized by a creative or constructive urge. Another synonym could be "when the muse sings" which alludes to the ancient Greek concept of the muse, goddesses of inspiration who imbued artists with creativity and insight. Similarly, "when the fire ignites" or "when the passion surges" suggest a sudden burst of energy or fervor. Ultimately, the choice of synonym will depend on the context and tone of the situation being described.