What is an inciting moment in the book 1984? before the rising action
I'm not sure what you mean by "inciting moment," but I guess the term refers to what "incites" the rest of the action, or what "incites" Winston to break the rules of the party in the first place. Following this definition, the very first inciting moment would be when he experienced desire for the book in which he writes his forbidden thoughts, for it is desire that the party wants to eradicate above all else. The desire for the book is a prelude to all of his other desires, including the desire to hope, and especially the desire to love and be loved. Here is how the narrator presents this moment:
"He had seen it lying in the window of a frowsy little junk-shop in a slummy quarter of the town . . . and had been stricken immediately by an overwhelming desire to possessit. Party members were supposed not to go into ordinary shops . . . but the rule was not strictly kept . . . . He had given a quick glance up and down the street and then had slipped inside and bought the book for two dollars fifty. At the time he was not conscious of wanting it for any particular purpose. He had carried it guiltily home in his briefcase. Even with nothing written in it, it was a compromising possession.”
All of the highlighted words call attention to the inciting nature, the transgressive nature, of this moment of wanting, and then acting on the want contrary to party rules.
I would say that an early inciting incident (or foreshadowing moment) is the game the Parson's children play, "Spies" in Part One, Chapter Two. The children's playacting involves the indictment of those who practice "thoughtcrime."
In later chapters, Winston knows he is guilty of "thoughtcrime." A thoughtcrime is any negative position, no matter how minor, that goes against the ruling Party. Going against the party is tanatmount to destruction. As Winston notes in his journal, "Thoughtcrime does not entail death. Thoughtcrime IS death".