I agree with Upallnight. AC problems should be left to someone trained but if you can't at least consider covering the basics. For me the suggestion is based on learning the hard way.

https://www.youtube.com/watch?v=Pdq8JAlct6s

Some of these cars have high and low refrigerant pressure cutoff switches. Sounds like the car may have a low pressure problem but after a while (engine heat?) the pressure builds up high enough to untrip the low pressure switch?

Get the pressures, take it to an auto AC specialist, or take it to the BMW dealer to diagnose. You've had the problem for a month now - my wife would have divorced me for cruel and unusual punishment!

Day 3 after adding more refrigerant. Still kicking in right away (about 30 seconds after cold start) and running like a champ. Very cold, no more intermittent working or not. Pressure still reading at 37psi on the low side. I hope my research and trial on my e53 with he same problem helps OP.
TLDR: If your AC is working intermittently and kicks on after you hit higher (4k rpm) you likely have low pressure and need to add some refrigerant.

:dunno: I think having the system drained, vacuumed (to test for leaks), and then recharged would have been my first course of action. They would have given you all the information you needed regarding low and high side pressures, leaking, etc. Cost here to have that done is ~$90.

If he lost enough refrigerant that the system is not operating correctly, then he must have a leak somewhere. Just adding refrigerant to a leaky system is NOT A Fix.

So I ended up having the compressor replaced at the AC shop. Cost right at $1500 and it seems to be working ok now. When I put the thermometer in the vent it cools about 30 degrees lower than the outside temp which I think is pretty normal. Want to thank everyone for taking time to help me with the diagnosis and steering me in the right direction.

^Good to hear. Pricey, but at least it's sorted.

Did the shop say if the compressor was not doing it's job or if it was leaking somewhere?

You can recover some of your costs by selling the spare aux. fan you now have. ;)

I assume your original aux. fan was fine and the diagnosis of a bad fan in your first post was incorrect...?

The compressor was just not performing but no leakage. I'm pretty sure the original aux fan was bad or at least that's what I'm telling myself LOL

Easy to test - you don't have to fit it, just connect the electrical connection. BUT make sure you secure it on top of the engine bay or wherever it's sitting - these things have some torque when they start and it could fly around and take off a finger - or worse! :rofl: