Web server slows down frequently

I am doing a website hosted at www.bettermercahnt.com
It is hosted on a dedicated server from godaddy.com on a windown2003 platform.
This is the one and only website hosted on the server, and still in
developing phase so there are no such user load (I can I am the only user who
browse).

Issue I am facing with the server request is that sometimes it replies
within 1-2 seconds but at some other time it gets slow down and takes 10-12
seconds to serve same page. It behaves same way for that time period and have
no affect even I referesh my browser 100's of time.

can someone help me with this issue?