Inspiron 15 7568 2-in-1, long black screen before Windows

I am facing a technical problem with my Inspiron 15 7568 2-in-1. Once I switch it on, it keep black screen for around 10-15 minute before starting into Windows.I have original Windows and recently updated. I appreciate if you could guide me and provide me a solution for this problem. I am student and all my work and studying depends on my laptop.

Thank and best regards