Question

I have a 2005 BMW 545i (rear wheel drive) automatic with 145,000 miles and I have 3 problems with the car.
1. Check engine light comes on. Sometimes it is the 1/2 yellow check engine light and other times it is the full yellow check engine light. When the full one is on the car goes into reduced power ( can't go more than 20-30mph). Then the light will go off if I turn the car off while driving and turn back on. Everything will be ok (no light for a few hours or even days). Or just letting the car sit for a while will make it ok for a while. Even after extended idling the light can come on. Sometimes the yellow round arrow warning light comes on at the same time.

2. At 40mph I can feel the car shifting in and out of gear. Before it was so smooth

3. The rear end at a complete stop and then accelerating will slip before the rear wheel engages. I get a banging sound from the back as the rear end finally engages. Changed the rear end fluid with BMW fluid a few time but no difference.