iPhone 4S sometimes loses contacts and then later comes back

Hi,

I've noticed that every month or two, my iPhone 4S running 7.1.1 will lose all but a few contacts (usually all but 5 or 6). Then, they will come back about 4-6 hours later and everything will be back to normal. The same happened today (although the contacts haven't come back yet) and I was wondering if anyone knew of a solution to preventing this from happening again and getting my contacts back right now. It's weird because all of the contacts are still in the Contacts application on my Macbook but they just disappear from my phone for a while every so often. I've tried quitting out of the Messages and Phone apps as well as restarting my iPhone, however none have worked. Could someone please help me?

Thank you!