MacBook Pro (Retina, 15-inch, Late 2013) takes 40 seconds on startup before the Apple logo appears

I have had my Macbook Pro (Late 2013) for just over a year now. Till last week, it worked flawlessly, would take just a couple of seconds from turning on till the Apple logo appears. However now it takes more than 40 seconds before the logo appears. I do not even have much on my hard disk (30% of its capacity is occupied). Is anyone facing the same problem and is it normal? I do not have Apple Care.