You wake up in the middle of the night to a vision like the one you see above you. Should you worry? Is your C31 about to explode?
Absolutely not. Everything is fine, and the bright flashing blue light is normal. Your C31 is getting an update. The flashing should go away in a few minutes and you will have the latest and greatest automatically.
Updates can come any time of the day or night and while they are infrequent, they bring stability and sometimes new features to your DIRECTV equipment. Nothing to be afraid of.