Slight Update
Wow. This happened to me last night, and I thought it was the weirdest thing. I wasn't even using my phone. It was sitting on my dinner table, and I noticed the screen on with the LG logo. I went over and picked it up. It stayed on the logo a few minutes, so I took the battery out. Then I turned it on, nothing but LG screen. I kept messing with it with a combination of Power/volume down and finally got it to come on to my home screen. It worked for about five minutes before being wonky again. I took the batter out all night. I'm hoping that I can get it to come on again today (I've tried 10 times and not been able to) so that I can make sure the developer options is checked, then I can hook it to the computer and mess around with it.
Thanks for this thread. It seems most of us just started having this issue in August. I'm planning on getting the V20 next month, but I need this one to last until then. haha Please keep us updated if anyone figures anything out and I will do the same.
SO, not saying this will help anything but, after messing around with the phone for several hours I've learned this:
If you take the battery out, then plug it into your laptop, then turn it on: a battery icon will pop up with a ? on it.
From there, if you hold down the VOLUME down key, and insert the battery, it will take you into the quick boot menu automatically. Unfortunately I never set that up, and not it will not allow me to set it up. I assumed I could get to safe mode from there. This is the first time I've seen where I would have to "set up" the quick boot menu. This is my first LG phone though. I usually use HTC, or MOTO.
Now, the more interesting thing is, begin as I did last time.
Phone off, battery out, plug into computer, power on. Then hold the UP volume key as you insert the battery and it will take you to your "Tethering" option. So for most of you that have this problem, maybe you will be able to get the data to back it up. Unfortunately for me, it tells me I have to do a Firmware update first, and to not unplug the USB connection until it is complete. If your firmware is up to date, maybe it will allow you to do back up (I thought my firmware was up to date, but guess not).
I hope this helps someone, and I do hope that someone can build on what I've done so far so we can figure out how to at least get our data off the phone.