If you don't have full voltage 100% of the time the computers (yes, there's more than one) will go nuts, and do all sorts of things and throw codes. Alternator and/or battery would be the first things to check (bad wiring in the charging system would be next). You pretty much answered your own question, when you're up to speed everything seems OK.

'99 Disco II
'95 R.R.C. Lwb (Gone...)
'76 Series III Hybrid 109
'70 Rover 3500S (Gone...)