My first attempt at doing this.
Tripod was braced in the car using one leg against the rear seat and the other two legs against the backs of the front seats. Aperture set to F/9.0, Aperture priority, ISO 320 so exposure times varied depending on ambient light. Focus locked and set to manual to avoid focus hunting. Shots were taken using my intervalometer. Set to take 60 or so shots with a 35 second delay in between (to allow for a potential 30 second shot if it happened).
This way, I could set the camera taking the shots, drive off and let the camera continue its work with no intervention from myself whilst driving. Also, the shots were taken at the legal speed limits.
Things to note.
I need to fix the composition (Centralise better and lower the camera down so there's less of if none at all of the rear view mirror.
I also need to perhaps decide on a specific exposure time to avoid blooming of the dash / stereo lights etc. and also, that definitely needs to be shorter. Probably 15 seconds or less whilst driving under brighter lights as opposed to no lights with just main beam as it doesn't light up any of the interior of the car.
Anyway, here's the best of the bunch. Some better than others
This one is probably the best in regards to the exposure on the dash lights.