2011 A8 Cluster and Mmi power loss

Hey guys so I own a 01 S4 and just the other day I bought my first newer Audi, my first 2011 Audi A8 4.2.

But the issue is that everything that that surrounds the driver, controls wise will intermittently shut down. The instrument cluster, the mmi, climate control and radio, stuff like that goes out. So in order to start the car I have to take everything out of the back and disconnect the battery (already bad because I hate that everything looses memory) and I have to connect and disconnect the negative until I see the cluster actually turn on, other wise all the car does is flash the white illumination lights on the cluster, no info or power, that’s it.

But when the dash does decide to come alive I jump in, start it, everything comes on, then I’ll tighten the clamp and go, every light and warning in the book will flash btw.

BUT if I start going it’s only a matter of time until everything just shuts off again, all of the controls, info and gauges, but yet the car will continue to drive and the transmission will still shift, the lights on the shifter stay on but the engine stop/start will have no light and I can’t turn the car back off. I have to pull a relay for it to turn off from there, or wait for the next time things turn on which could be awhile.

Any ideas on what could cause all of these controls and such to just shut off whenever they want?

Things that DO always work are ambient lighting, seats, windows… Things that DONT work are mmi, gauges, key controls, trunk pop…