I’m having the same problem.
I left my Q with the battery inside for 2 month or so. I wanted to take it out so I checked the battery. The battery icon was missing the left triangle indicating that the battery was not fully charge. I took the battery out and charged it.
The camera never turn on again. I tried everything I could remember.
Yesterday after reading this post I tried once again and the camera turn on for the very first time in 2 months. After I’ve turn it off it didn’t turn on again!
Today I tried to warm up the battery and the camera turn on again. But once again after I turn it off it doesn’t start up again.
I’ve able to replicate this three times.
Now I’m recording a second 25 min video. I’m trying to completely drain the battery and then recharge it to see what happens.
Apparently this is a battery issue. Better than a dead camera