Now after couple starts she does not start at all, all lights flicker, radio dies. Previous to this she starts & within minute all systems start to die down, rpm starts to fluctuate then I just turned her off. Left side xenon headlight also shut down, hope not burnt out. No way drive her now. Battery still good 13V. Towing to dealer next week. Will keep posted. Thanks for help.

Grounds
 

One other thing to check. There should be a main grounding wire that connects from the engine to the chassis. On my 01 it is on the passenger side behind the wheel. If you crawl under it you should be able to locate it. It needs to be clean and tight. With the battery in the back of the car the ground wire is very important. Also, have you done a voltage check with it running from the jump post in the engine compartment to the engine/chassis? I know it is tough without it running. You could also take one of your jumper cables and connect it to somewhere on the chassis and the other to a bolt on the engine and see what happens. If it starts, you know you have a grounding issue.

Ok. Checked the grounding cable under the wheel well, all fine. Then I thought about battery, so started charging w/a charger & it didn't charge for a very long time, it was 4 yrs old. It's winter, so went ahead bought a new H7/94R charged fully & installed & started, now everything fine. All systems on, car moved back & forth, didn't go for test drive. BUT, only the battery & 4x4 warning on, which I think means as you said very 1st, charging system problem. Tomorrow I'm going to test drive to make sure the gear shifting is fine, which will rule out transmission fluid change issues. So, I'm leaning toward co-incident charging system problem, not transmission shock. Thanks for help. I still plan to take to dealer for a full diagnostic check. I have an extended warranty plan.

Progress
 

I am glad you made progress, but if battery light is still on, you need to check the voltage at the battery with the engine running. You can take it for a "test" drive, but get all systems working first than you will be getting a true idea of what is going on during your test. Pretty sure you alternator is dead due to trying to maintain an old battery. Your voltage with the engine running should be 13+volts.

Checked V before & after starting: 12.59 dropped to 11.89 when running. After engine stopped, 12.29. So 100% Alternator not charging. Haven't dared to test drive yet w/V dropped after 1 crank. Now charging battery again & will try short test drive.

Not sure why you are dead set on driving it without all systems up and operating correctly. Please understand that the X has many electrical demands on it when operating. IF the battery isn't charging and the alternator isn't putting out 13+volts, you could potentialy have issues just doing a short drive. I know you want to rule out the tranny issues, but get it up and running properly.

Dealer found 3 problems- A) Alternator of course, B) Fuel pump relay code 0045(although never had any fuel system problem & car was driving fine) & C)Upper left rear control arm (unrelated) & Also a fault code for transfercase module & power supply but say might be related to failed alternator.

as for the fault code the dealer found and saying it might be related to alt is a good possibility.

Finally alternator, left rear upper control arm & fuel pump relay replace, X5 runs great. No ATF fluid issues. Definite improvement in shifting, the lurches disappeared.......BMW calls it a lifetime fluid.....no way!
Other issue came up rear left tail light power harness connector ground (brown) wire burned, tail light don't work at all now. Does anyone know how to replace the wiring harness connector?

could make your own connector or you might be able to find a harness online?