iPhone 5c reboots itself after 3 minutes and battery % doesn't change

I have just upgraded my iPhone 5c to iOS 8.4 and my phone started acting wired its rebooting itself after 3-5 min when ever I am charging my phone and my battery usage is not being displayed properly it shows 100% all the time even after using it for 4-5 hrs. Recently I have also notice that when ever i shake my phone there is a strange sound coming out of my phone like something is dislodged in my phone. Could this be a problem with battery or something else or do I have to replace my old battery.