Hi Krishna,
All resources start preloading as soon as your participants open your experiment’s page, so you can’t preload earlier than that. Having welcome screens, consent forms, etc. at the very beginning gives time for the resources to preload in the background before participants reach a trial that uses a resource
I am not sure where the delay might be coming from in your case, but feel free to share your project’s demonstration link here or at support@pcibex.net
Jeremy