If the second time is much faster, your PC is slowly reclaiming a chunk of memory for use by Safari. If it takes 15 seconds both times, scan your hard disk for errors.
I have a windows XP machine and prefer to use Safari over Firefox but Safari takes 35 seconds to load the first time and 15 seconds the second time. (as instructed from you Reverse_Parn.) Firefox loads in 7 seconds. I have a imac running safari and it load very fast. Reverse_Parn, in layman's terms, why does Safari on the windows need so much time? And is that typical for a windows machine running safari? The reason I prefer safari over firefox is the font smoothing. I looked and couldn't find a font smoothing plug in for Firefox.
My Safari on a PC-WinXP takes around 60 seconds to load plus I get a message that the script in the URL is causing it to be slow loading and I have tried several tasks to improve this all to no avail.