Preheat the oven to 325°F (160°C). Grease the springform pan and line the bottom with parchment paper.
In a mixing bowl, combine the graham cracker crumbs, melted butter, and sugar for the crust. Mix until well combined and resembles wet sand.
Press the crumb mixture evenly into the bottom of the prepared springform pan. Bake for 10 minutes, then remove from the oven and let cool.
In a large mixing bowl, beat the softened cream cheese and sugar together using an electric mixer on medium speed until smooth and creamy.
Add the sour cream, eggs, eggnog, vanilla extract, nutmeg, cinnamon, and flour. Mix on low speed until just combined, being careful not to overmix.
Pour the cheesecake filling over the cooled crust, smoothing the top with a rubber spatula.
Place the springform pan inside a larger baking pan filled with hot water (this water bath helps cook the cheesecake evenly and prevents cracking).
Bake in the preheated oven for 60 minutes or until the edges are set but the center is slightly jiggly.
Turn off the oven and crack the oven door, allowing the cheesecake to cool slowly inside for 1 hour.
After cooling, remove the cheesecake from the oven and water bath. Refrigerate for at least 4 hours or overnight before serving.
Before serving, top with whipped cream and sprinkle with grated nutmeg or cinnamon, if desired.