Hi @all!
Somehow I'm really "glad" at the moment to read your stories 😕
For about 1 1/2 week now I'm experiencing the same with my iPad Air 1 und iOS 11.
During this time I did some search through the forums but couldn't find anything similar to my issue, so I started wondering if my battery is broken.
After read your issues, I can tell that everything is "ok", at least with my battery.
It just seems as if my iPad doesn't like current any more...
Usually I drain my iPad's battery really low and afterwards charge it (12W wall plug).
After connecting to the charger it takes some time until the iPad has enough battery to start up.
However, what comes after this start up is a bootloop 😠
The iPad boots until the charging sound is audible, then it is stuck with the Apple icon until it reboots, and so on.
During this process the iPad heats up and also drains battery, so the battery all in all isn't charged and the iPad dies on low battery, although it is connected to the charger 😁
If one is really lucky, then iPad will stop trying to boot after several attempts (can take hours...) or one can somehow stop the iPad manually from booting.
Then the battery can be charged without directly burning all the energy during bootloops.
After some time, when one thinks the battery might be fully charged, one can try to boot the device again.
If this booting is down while still connected to the charger, one will end hearing the charge sound and seeing the Apple logo.
To not end in bootloop again, one either has to disconnect the charger immediately after the sound was played or directly boot without a charger connected to the device.
I really hope, that Apple will release an new preview without this bug next week.
Until that, I live with the procedure I figured out, knowing that I'm not the only one...
Hope this somehow helps you guys, too!