I just had the strangest experience with my Moto X. Last night I was not able to get to the passcode screen on my phone. I would slide the unlock button down and end up at a blank screen. Same thing happened when I pressed the power button, and there was nothing it seemed I could do to fix the problem.
First, I tried rebooting the phone in safe mode, thinking the problem had to do with an IFTTT recipe I had created to change the wallpaper based on an Instagram hashtag. My theory was that there were so many notifications coming into my phone, it was giving Active Display fits.
The IFTTT rule may have been the problem, but I don't know for sure. What I do know is that rebooting in safe mode did no good. In fact, it was worse, all I got was a blank screen with the Safe Mode label shown at the bottom left.
My next step was to wipe the cache partition. Turns out that the instructions that Motorola provides for wiping the cache partition is incorrect for those with Lollipop installed on their Moto X. If you have Lollipop on your Moto X then step 5 in the instructions is wrong, instead press the Power button for 2-3 seconds and then press Volume Up.
Alas, wiping the cache partition also did not fix my problem last night. At this point I did not know what to do, so I posted a query on Motorola's forum (which still hasn't been responded to) charged up the phone and went to bed resolved that today I would have to completely wipe the phone with a factory reset.
To my surprise, it seems that what I needed to do was leave the phone alone for several hours. When I got up this morning and turned the phone on, it successfully booted up and provided the passcode screen so I could enter my PIN. I have not wiped the phone, but I have found that the cache partition wipe did happen as I have had to log back in to all the services I've been using on the phone. I've also managed to lose two home screens in the process, but in general the phone seems to be working as expected.
A full factory wipe may still be in the future for my Moto X, but for the moment I am just happy to have my phone operating.