My car does it too. It seems to be a normal ETA thing these days. It's the timing reference sensor, or the engine speed sensor one of the two on the bellhousing of the tranny.
91 318is - M50NV (gone)
02 WRB Subaru WRX EJ207 forged, 320 AWHP stock turbo.
85 - 325
02 325i Sedan