Idel start car to idel runs at 2000rpms then 30 second later drops 1000rpm back to 2000 up and down up and down dude its driving me crazy

I would replace the spark plug wires and spark plugs first and verify correct fuel pressure. Also do an OBD1 fault code test. You can do this test by turning the ignition key to run and then off and then to ruin and off then to run and wait for check engine light to blink out codes, codes will be a number of flashes and a pause and then more, for instance 4 blinks and then pause and 3 blinks, that is fault code 43

Did you hook up a pressure gauge as I asked? What where the results?

Monitor the fuel pressure when this happens.

All the above is normal , except 2000rpm is a little high at idle . can be adjusted down to 1500rpm. the computer adjusts the engine speed . in drive the transmission loads up the engine idle drops to 1000rpm . in park engine unloaded rpm increase all normal.

When the weather is warm, we rely on our car's cooling system to keep temperatures in the engine compartment under control, and keep us on the road. Your cooling system is a series of components that circulate coolant through the engine to absorb heat, then circulate air around the coolant to get it out. If any part of the system stops working, you're on the side of the road while your engine takes a steam bath.The best medicine is preventive. You should flush your radiator on schedule to keep the system clean and well flowing. Unfortunately we aren't always lucky, and things go wrong. Let us help you figure out why your car or truck is running hot or overheating.
Problem with 2000 BMW 528i idling problem when you start the car in the winter time. The care starts by idling aroun 1000rpm, which is normal for a cold engine start, but within 30 seconds it drops down to about 750rpm. Now the problem is that it fluctuates between 750rpm and 250rpm, almost shutting down, and sometimes does shutdown.
Solutions:
1. I would first try to clean out the Idle control valve...some people have seen a 30% increase on cold start idle, there are several links in the DIY section.

2. If the sounds like classic Vanos seal issues. I had the same problem with mine in the cold weather. It would go away after the car warmed up. Replaced the Vanos seals and the problem disappeared.
3. Make sure you get the correct replacement seals or you'll end up with the same problem down the road.

replace the crankshaft position sensor

Clean MAF Sensor

Check for vacuum leaks

Check Air Idle Control Solenoid,
if you have one

Clean throttle body plate

Change the oil pressure sender -- most likely defective

idel air control motor is compisating for a stall you might need to clean throttle plate and check for vacume leaks

This almost sounds like the fuel pump check valve is leaking back during the day. Try this to see if it helps. Before you start your car during the day, cycle the key on and off a few times first. This runs the pump for a few seconds and builds up fuel pressure. If it starts immediately after the key cycling, that is most likely your problem.