I have a seven year old GSD female that has taken to barking at anything and anybody from the car.  Stop the car and open the tailgate and she stops.  No other problems with her at all.  Any ideas please.

Is she hot? I don't know about the UK but in canada theres a heat wave!

No she was doing it in the sub zero conditions also - does it even after a long cool swim while she is still damp in the car.  All the time - without fail.

Attention seeking & it is working ! is she crated in the car(the safest way IMHO) ? if so cover the crate, turn up the radio & ignore

She does it when the car is parked and no one is around.  Have been ignoring it completely but she has started to bark at everything now - fire hydrants, post boxes you name it.  Never does it outside of the car.  Just noticed she will not let our friends dog in the car.  We have to let him in first then she jumps in and is OK.  That is a new development so it may be territorial.  Maybe she is getting crabby with age. It happens !! Otherwise she is sweetness and light.

If it's only started recently, you might want to check to see if there are any joint problems starting to arise. The jostling of the car can make them uncomfortable. Just something to check.

The vet checked her out thoroughly and a breeder friend of mine thinks its territorial.  Tried a fun trick of his over the weekend and it worked but will persevere and see if its a long term solution for us before I share it. Certainly relatively unorthodox.  Wary of the reaction I might get on the board !!