Q: My car makes a very odd beeping noise, what gives?

75% of the time I start my car I have this issue, and its either all or nothing: I unlock the car, get in, hold my clutch in, take it out of gear (parking brake still on) and crank over the starter, the engine starts fine but I hear 5-6 very fast and loud beeps. The beeps will repeat once I am releasing the clutch and giving it gas to take off, and sometimes when I'm about 20 feet from my parking space in first gear but only on those three instances will it ever do the beeping. Now, its not every drive cycle, but most of them. It is not only on cold starts. It is not the "hourly" BMW beep nor the "excessively cold/hot weather " BMW beep, I have searched hundreds of times for the answer and it seems nobody else has run across this (from what I've seen). Please help!

My car has 155900 miles.
My car has a manual transmission.