Help with strange elec/starting issue please...

[the_cueball]

I've put this in general, just in case it's not car specific and someone with an Audi has had this issue before...but if it matters, the problem is a 2003 (D2) S8.

So, the car starts fine, drives, turns and stops fine... no issues, no warning lights, no issues with the scan.

I'll drive it about, then stop... let's say to go to the bank.

then I come back out to the car, and it's dead.... it will not start, no crank, no splutters - nothing.

the lights and radio work fine though.

at first it thought it sounds like the battery isn't getting charged by the alternator..... but......

if I leave the car overnight, it starts fine, first time with no issues! I don't understand it.

the battery is pretty new and I've had it on trickle charge
I've redone the key and matched it to the car (thinking it may be the immobiliser)

anyone had this before?!? I can't keep leaving the car overnight when I go places! lol

 

[NHN]

I would be checking starter circuit as immo cuts engine after few seconds running, so I doubt its immo.