Alright, here goes.

My device have entered some weird bootloop, and I haven't even started fiddling with it.

Had it in the charger over night, in the morning it just reboot's all the time.

It boots up, shows the Jolla logo; then the led turns red and it reboots. Again and again.

Anyone got some pointers, so I can get the device running again :-)

1) What charger did you use?

2) Did you enable developer mode at any point and if so, what did you (exactly) do with it?

3) What SW version are you on?

Also, 4) Are you in any way trying to use the device without a battery in it

1) The device ran out of battery the night before, and I charged it with a charger from an iPhone which was available were I was at the time. Put it in the charger when at home, using the charger from my Nokia N900, which I have been using all the time since I got the device.

2) Yes, I enabled it, connected to the device through ssh; thats all. Didn't do anything else than that.

3) The most recent - 10.0.1.12

4) No, the only thing I can think of; is that I pulled the battery out at some point without shutting the device down.

USB or Charger connected at that point?

Pulled the battery out, took out the sim; put the battery in again, and then connected the charger.

Is there something I can do to get the device running again; or provide additional information ?

If you show up in #jollamobile on irc.freenode.net, you might be able to find some people to help you further diagnose.

Do you have a Linux PC?

I'll show up there.

I have a Mac, will that do ?

Do you have a hunch of what has happend ?

I had this issue few times with my N9.

What's happening is your battery is too low to boot up the kernel up to charge the phones battery, so it will keep in the loop but never start up.

the way I fixed it for my N9 is using the flasher, it somehow allowed to get more power the from USB and actually charged up the device.

Check these posts out:

first
second

and for flashing info read this thread