My X is less than 24 hours old. I have not rooted it and have only put on one of the recommended launchers from here and a few other standard apps (like Pandora). I did the update earlier today as well.
It has probably restarted 12 times today. A couple times while playing with Pandora, once while texting and then on its own as well.
I've searched the forums and saw some others with the same issue but it looked like they had all rooted theirs, so I was checking to see if I am having a different problem.