Is there any update on the story ?
I too used a car charger to get my phone into this state. My reboot loop is like:

1.black screen-> 2.yellow light slowly blinks twice (like it were charging battery)-> 3. one really really short blink of green light -> 4. dim Nokia logo and dark background -> 5. running dots (like it was gonna launch the bootscreen) lasts maybe 4 seconds- > 6. black screen again for maybe 4~5 seconds

it would keep looping for who knows how long. However, I could still bootup if I try to hold down the power button for a few times in a loop at stage6.

The micro usb port has a weird behavior now. It would only prompt ONCE for selecting mass storage mode/pc suit mode when plugged. Subsequent unplug/plug of usb cable would only charge and display charging messages.

The loop starts again after I switch it off. The ONLY way to stop it is to take out the battery.