So happy to this forum
My Z4 started fine in morning parked at work, all day busy - got to car to fire up and it felt like weak battery
Well tapping, hitting or smashing with rubber hamme rid no change to my issue
Removed and charged battery overnight, walked home and back, now starter is worse - barely a click now, all electrics still work just perfect.
I read this forum, all point to starter motor - europarts day later, £59 later and some acrobatics to remove it (mine was stuck on midd pin, just would not move backwards) - replaced starter and works like a dream.
Will try to service old BMW starter and maybe replace it back for Starline I fitted