Buying a car for short-term use as an expatriate

Is it straight-forward for an expat to purchase a cheap German plate car and register it easily on German (non-export) plates?

In my case I am only here for a few months before changing country with work...

I don't have any German papers at all yet, as my trip was only extended today... will I need some kind of foreigner ID number or address certificate, and in that case could a long-term apartment hotel address be used?

Any advice greatly appreciated. Thanks!

You need to be resident (i.e. have made your Anmeldung) because this is required to get insurance, without which you cannot register your car. Even if you faked this, you still need to show your piece of paper showing your address registration.
Your only (legal) option would be to register it on export plates but that gives you only a very limited time.

You neither need to be registered nor resident to get insurance, but it won't be cheap. You DO need to be registered to get the car registered (and the plates). It doesn't need to be you who registers the car - a friend, colleague or neighbour could register it for you. Easiest and cheapest all round is to get the residency paperwork...

Please check this first...
Once you could (for example) use a UK registered car for a year in Germany,
take it back to the UK - get it MOT tested and UK VE Duty paid and use it for another year in
Germany (I did this for years).
Now you can use another EU registered car in Germany for 6 months in any one year.
(Stops what I once did).
It really is a hassle to get a car of non German origin registered in D - avoid it if you can.
It is not a great problem to export a car from Germany (you need special plates and insurance)
but why bother?

Do you really need a car that badly? In this country there are so many options available for transport without having to go through the hassle and expense of owning a car. Really, think it over. I had a great experience recently with a website that links up drivers with passengers. There are other sites that help you too, so you don't have to rely on Deutsche Bahn over the next few strike-filled months either. Renting is often expensive but unless you need the car every day, it won't add up to as much as you'll pay on the used car, registration, taxes, license and on and on and on.

And remember the StattAuto or the equivalent car-sharing scheme in your town/city.

Today I had my German car TUV'd and registered it for the first time in my name.
You need your passport and the Bescheinigung from the Anmeldungsamt
which quotes your passport no. and address.
You also need the car reg. document and the little paper details thing
(without which no garage will look at your car).
Plus insurance certificate and TUV/AU certificate.
If you move areas you need new plates - there are shops selling them
(usually) near the Zulassungsamt (Registration Office).
This was in Hamburg - the whole thing took two hours.
Had the TUV done by DEKRA (more lenient IMHO) and drove 5 km
to the Zulassungsamt.
In HH you get a separate bill for the Road Tax.
Fees at the Zulassungsamt payable by credit card or cash (into a natty machine).
You can get clamped if you don't pay your Road Tax bill (I know a lady who does this for a living..).
I've a German helper - despite being pretty fluent in German I would have had probs.
getting the paperwork sorted out ready without her help.
You do not need much German for the TUV or Registration.
Knowing that Bar means cash helps 'tho!

Ouch - thats like saying buying a VW from Opel...

TUV & DEKRA are opposing companies! The TÜV would like you to think that they are THE automatic choice (just like using word Hoover for vacuum cleaner).

What you mean to say is HU (Hauptuntersuchung) done by DEKRA.
Look at your car - it has a HU sticker & not a TÜV sticker.

HEM, you are quite right.
Except that they are not really "companies" - "Verein" is difficult to translate.
My partner (German) uses TÜV as a general term as do a lot of Germans of my acquaintance.
It seems to be the preferred term in the press too.
They are supposed to test to a uniform standard - but I noticed that DEKRA are
not so stringent (as you say - competition) - two years ago they missed a notifiable
defect.