Hi - new member so sorry if it's already been asked!

My A6 2.5tDI quattro - showed a lower battery voltage than normal yesterday when starting and there was no power steering. When trying to drive it home I parked up and turned the engine off. the car started back up fine but still the same issues ..... then whilst completing the journey (2miles) everything suddenly came back to life - PAS and no battery light!

Now today, earlier it was fine but the second time I went to use the car during the day it showed the same issues as above, only this time the car does not turn on after ignition is turned off.

Not too sure if it's related but I went to get the wheels aligned yesterday and when I initially had the car back the ABS and ESP lights were coming on. I took it straight back and then re-did the alignment which seemed to make the lights turn off!

Looking for pointers on what it could be

Thanks