I have had a couple of similar occurrences in the 7 years I have had my RRS. As I understand it, if the battery starts getting a bit low the car goes into a power saving mode that generally the driver is not aware of. The obvious thing is though, the radio - the first stage the volume is restricted and a message comes up on the radio screen something like "Low Power Mode" after driving for a while it goes away and full volume is available - I guess the battery is charged back up and the car goes out of low power mode. I have had this Low Power Mode a few times with my old battery but not in the past 12 months with a newbattery.
Twice I had something resembling what you had - radio seems to be on - but no volume or display. Driving around does not seem to fix it initially but some time later the radio is back all ok - I understand this is a lower level of power saving mode. Again I have not had this with my new battery.
I have looked in the handbook for this "Low Power Mode" on the radio and not found anything. I gleaned the above information from discussion on the UK D3 site a couple of years back so cannot confirm how valid it is.
Garry
REMLR 243
2007 Range Rover Sport TDV6
1977 FC 101
1976 Jaguar XJ12C
1973 Haflinger AP700
1971 Jaguar V12 E-Type Series 3 Roadster
1957 Series 1 88"
1957 Series 1 88" Station Wagon
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