restore from cloud

I recently got a new Mac book and just today I woke up to my phone being almost erased, my screen appeared like it had rested at first then it displayed the words "restoring from icloud" after a while I had to type my iCloud password and open my phone to all of my old apps being downloaded and my custom phone settings (ie: text size, display etc) being removed and back to the default settings. what could have caused this?