2003 Audi A6 Quattro

I have a problem with the gear indicator , when I start the engine and put the stick on D everything is normal but when I put it in reverse and back to D all the indicator lights is all on and when I start to accelerate it hesitate tremendously like it has very little power or as if the fluid is low but after powering the motor off a restarting is fine. Sometimes when I powered the car off it seems as if the battery is dead but after a few times or opening the door up hitting the break it will crank again. Imagine pulling out on the highway and the car is not accelerating. Please help 😫