Can't say I've ever noticed that on my 335 either.
Is the car for sale at a bmw dealership? If it is and you really like the car then I wouldn't worry too much, it will have a auc warranty which is very good.
2008 E90 330i - Gone
2010 E91 335D - Gone
2014 Audi S4 - Sooooooooo much better than the BMW's and so wish I new this before!