hi
your problem - your iPhone loads music very slow
MY QUESTION.
are you using iTunes or other 3 party app. for listenings music
if you are using iTunes then you need to contact apple support for further details
as your problem is very rare or is your phone is 16 gb and with less space left
that could be the problem
APPLE SUPPORT -----http://www.apple.com/support/contact/
hope i helped you
HAVE A GREAT DAY!