Why is Android phone shutting down by itself? Phone is Samsung Infuse 4G with Cyanogenmod 11 (Android 4.4). On a few recent occasions when I check it in the morning, I find that it's powered off. I start it up again, and it shows plenty of battery charge (75% or more). Is there a log or something that I can look at that would explain why it has shut down?
Well, it's well known problem for Samsung phones and tablets:

Read carefully: http://androidforums.com/threads/randomly-turning-off.312084/

One of possible solution (cited from above post):


  I found another workaround, turning off sleep mode. Maybe there are
  easier ways to do it, but i did it like this:
  
  (copied the instructions from another forum):
  
  
  Download and install a free app Load Monitor. 
  Under its preferences check the following on... 
  Add Notification, Only notify high load, Auto start, and most importantly Wake Lock. 
  
  
  The wake lock prevents the phone from going into sleep mode, now i'm
  already 24 hours without shutdowns. I also set the update interval to
  2 hours for the Load monitor, so it doesn't bug me often.
  
  The downside must be battery consumption, i assume that the sleep mode
  does save up some juice. But at the moment i'd rather worry for the
  battery than if the phone is on or not. :)
  
  Also, this problem is not limited to galaxy ace.. A little searching
  with google revealed that there is even a class action lawsuit against
  Samsung because of the same problem in Samsung S models.


Hope it Help