my problem was a clutch sensor when there was no click or sign of the starter. Ive also one time one the m3 had a bad BST cable.
But narrow it down until you have the starter to replace.
"So I'm drifting away like a feather in air, letting my soul take me away from the hurt and despair.
So I'm, keepin' it vertical forever elevator, riding the escalator to something that is greater.."
Official E46 OT Podcast