iPhone random restart

Hello! I was browsing the web when my screen suddenly went black. Then the phone restarted and everything seems to be normal. I know that sometimes iphones may restart randomly and I've found various ways to solve this, but I've read somewhere to check my analytics data.

There I've found "backboardd.wakeups_resource..." and "ExcUserFault_wifid_..." being the last ones. When I searched for backboardd I've noticed discussions about malware and this determined me to post this questions:

Can my iphone be infected with some malware or virus? Can the site I was browsing cause the restart?

My phone is NOT jailbroken and everything installed comes from AppStore.

Thanks!