BMW Repair: 1997 523i Auto, valve seals, bmw history

Question
My BMW 523i chucks out blue smoke when started from cold for about 20 - 30 seconds. After this no smoke (that i can see) comes out. Engine sounds ok, ie no rattles and the power delivery is fine when driving. It never misses a beat! When it is started from hot no smoke comes out. The smoke smells a bit like burning plastic. Has done 70000 miles and has full BMW history. I have changed the oil and filter to no avail.

Answer
We dont have 523's here in the USA so Im not familiar with them.
I would guess the exhaust valve seals are letting a little oil by when they cool down and shrink a little.
You either need new seals or an oil additive to try and soften and swell them.If the guides are worn then a valve job is on your to-do list.