Hi Volgerle,
I only could give some rather profan ideas to your dream-symbols like cars and bikes, cause I unfortunately dont know well the translation of such symbols into higher realms or bodies, but surely you`ll get some good answers from the others here.
From certain dream-symbol-schools and as well from my own dream-symbols related to reality I know that those vehicles can be assigned, due to their amount of wheels, to differen forms of relationships. So when you look at a 4 wheels car then one would relate it to a family or a group or friendships, and when a 2 wheels vehicle occurs it would be assigned to more personal intimate relationships, like a couple. As in your latest dreams both sorts of wheel-vehicles occur it might have to do something with both, or even a conflict between friendship and "coupleship" (dont know the word), so but then this yet would be an interpretation of mine but of course its only you who can know or investigate if these vehicle-dreams have something to do with relationships in general or at all for you.
In any case a vehicel for me is a symbol for potenital development. Though also I agree in that a message could be to make all a bit slower, at least not be rushing through or for anything. And finally I think the message could be to just get some things in order and done to be able to develop to a certain further destiny.

greetings, Istia