Have the same issue on my Note 3. Got the EU-version which means, there was no region lock by default. After juggling around with it a few days I had flashed Omega Custom ROM as it got vanilla installer to remove almost all bloatware from Samsung and Google. It was then really sleek, because fewer services were running in the background.
Now, after performing several updates from Omega (including some on 4.4.2), I got the same problem as you. My phone keeps restarting randomly, even by not touching it. I recognized, that after reboot completes, Google is perfoming more or less necessarily updates. I guess Play Store can perform updates after an restart only. So I still don't know whether to switch off automatic updates, as iOS is offering this feature. This would propably help out.
Another fact is, by loading the phone's battery shortly and often in a row (i.e. by attaching, disconnecting and reattatching it to your computer very often) this could interrupt the charge balancing controller. So, the stored battery values aren't matching with the real ones, which causes in lag or vary of battery power supply. At a specific point Android forces an shutdown or reboot in order to refresh the actual battery values. On iOS this was noticable, as remaining battery percentage was slightly different after a reboot. There the percentage dropped suddenly by a bigger amount, then rested on that value a couple of minutes before shutting down. After a reboot, mostly the value then was higher again. Strange behaviour.
I recommend the 6 state charging: Unload battery under 5 %, then charge to 80%, let it drop to 20%, charge it to 80% again, let it drop under 5% and at least charge until it's full. Apple is advising an alternate method in order to store batteries for long time. So this is a mixture of best methods.
Maybe wiping dalvik cache and cache partition help if reboot results from a specific app you're using. If being unsure, make backup of your entire phone by using Titanium or Helium and perform an full wipe afterwards. This methods would assume, you have a custom recovery partition on your phone as by default you're not able to perform wipes on your own. You should not do so, if you don't know anything about custom recovery and custom firmwares.
Let me know, if anything helped out

As I am from Germany, please forgive my old school english
Nice greets, Chris