Why does my iPhone keep deleting my contacts?

Hi, about once a week my phone has a complete epi and deletes all my phone contacts! I will just go on my phone one day and my phonebook says 'no contacts'.It's so annoying because when I try to do a computer back up to regain the information it takes hours. Is there some sort of reboot I can do that will solve the problem but won't delete all my phones data? Or does it need some sort of professional repair? Thanks for your suggestions

Take it into your iPhone company. (AT&T, Verizon etc… )

Because its an Iphone… Get a HTC One, or Galaxy S4 and all of your troubles will go away.

I love apple computers but other devices I can't stand.