Over the past month I too started getting a lot of random reboots, 2-3 per day. but one thing that has helped is uninstalling all the google+ app updates.
after i uninstalled the updates i lasted 24 hours without a reboot. finally had one this morning. now i disabled the google+ app completely to see if that helps further.
i got this idea by looking at my wife's gnex, which has an uptime of over 400 hours. she doesn't bother updating any of her apps and i noticed that google+ was still on the original version.
my phone still crashes when browsing, which is more annoying, but the reboots when i'm not using the phone seem to be less frequent.