Yeah it could be a ton of things. Prob not the crankshaft itself but the crankshaft positioning sensor. Scan for codes otherwise you'll land up just throwing parts at it.
Montego Blue E90 335i
7" VRSF IC | OFT Tune | DCI | RB PCV | Secondary CAT Delete & CYBA 3.75" Tips | M3 Front | CSL Trunk | 19" LC Dyna Wheels