Freezes and random reboots

[DevilInPgh]

Since I updated to Kitkat, I've noticed some random reboots and have had to do a factory restore once when, after switching to ART, the phone froze on "Optimizing app 1 of 1". Overnight, I noticed that the phone froze (pressing the power button did nothing). So I did a simulated battery pull, and it took a few tries before I got the splash screen. After the animation, the screen went black again. After trying another simulated battery pull (but then noticing that it took a screenshot instead), I saw that the screen was instead black. It took a few seconds to get the screen working, but now it works, and reboots that I make seem to be fine. This, however, has me concerned about my phone. Has anyone else noticed these things after the Kitkat update, and do you know what to do to fix these?