Having also the freezing problem with my S3. So far I have tested numerous ways trying to figure out what is causing the phone to freeze. Last time I have used the Dummy File Generator without the phone freezing while filling up the memory. My S3 never freezes or shuts down when I am doing something with it. It's always the same situation, the phone has not been used for a while and when trying to wake it up it's just blinking dimmed blue light slowly and the screen stays black. I need to reboot the phone by pressing power button for a few seconds.
I have had the phone for over two years now and I have always used the stock firmware. No rooting or anything. At the end of summer I received a phone software update and some weeks after that my S3 started to freeze. First I thought I had a bad battery and replaced it, but freezing continued. It was like once a day or two it froze.
Well then, yesterday I uploaded the firmware using Kies in hope to solve the problem some people have been suggesting on other forums. That went okay and the phone lived, but on the next morning, today, the phone was frozen again. Blue blinking and black screen. This time I went to recovery mode and made a reset once again for the phone (Factory defaults + data/cache wipe/clean). Well well, the phone starts normally as before but this time after the basic setup, the phone notifies that there is an software update available. This is just my speculation, but this is the update after I started to have issues so I am not going to install it as long as my phone is working ok.
Some notes now after using the phone today for more than twelve hours. It is working silky smooth and has not frozen since morning. So, this is
ongoing research if it is some kind of software update issue. If the phone is working from now on, It must be the update that messes up something. I am using the same applications as before.
One thing about the update I now have on the hold, there is no information what it does, no "release number" or anything I could check somewhere else what is improved in this update. I'll let you know if the phone freezes again or it just keeps going on like it did before.