The first time you start the Quickstart, it creates an entire JCR-compliant repository in the background, which can take several minutes. After this initial startup, subsequent startups are much quicker as the repository infrastructure has already been laid down. Many startup options (such as the active port number and whether the AEM instance in question should be a Publish instance versus an Author instance; and much more) can be controlled by appropriately renaming the Quickstart file.