What caliber did you get it in? It's possible that a stiffer spring for .40 S&W or .357 SIG is in place and if it is chambered for 9mm it will be heavy. It's also possible that it is an aftermarket spring.
You can manually cock the hammer prior to racking the slide to make things easier. You may also consider calling SIG Customer Service regarding your concerns. If the wrong spring is in there they will likely replace it for free. I do NOT speak for SiG but this doesn't rate very high on the major malfunction chart by comparison to other problems that have and can be repoted.