I know this is late but I discovered a fix for the LG G3 "blue screen of death" looping restart problem. It does not require taking the phone apart (just remove the back, battery, sim and SD) and you won't lose your data. Here's how its done:
1. Take the back off the phone, remove the battery, SIM and SD cards.
2. Tape a thin piece of cardboard or tissue to protect sensitive areas (speaker, on/off button,
volume buttons, camera lens, IR eye, flash led). The process requires high heat.
3. Use a hairdryer on high heat and blow the heat over the uncovered areas for
ten (10) minutes.
>>>Do not hold the hairdryer in any one place for more than 15 sec.
>>> Do not use the hairdryer on the screen side of the phone.
4. After 10 minutes, allow the phone to cool from hot to just very warm.
5. Replace the battery without the SIM or SD cards inserted, and turn on the phone.
Your phone should come on to the normal opening screen.
>>>It may take about 2 minutes longer than usual for your phone to startup.
>>>Repeat the heating process if it doesn't work the first time.
Let your phone get a little hotter and do not let it cool as much before starting up.
6. After you get your phone working, turn it off, replace your SIM and SD cards and restart.
I don't know yet if this is a permanent fix so you should backup all your photos,
files and downloads in case the "blue screen of (almost) death" returns.
It worked for me - Hope this works for you!
God bless,
D. Swarn