Check for any air leaks, after a recent rolling road on my S1, the brake servo pipe worked loose and the car was almost impossible to start and when it did it died on tickover - I thought `hang on it`s not supposed to be like this` AFTER a rolling road, then we noticed the loose pipe, tightened it up and hey presto!!

Check for any loose pipes, tighten your jubilee clips on all the pipes etc.