Sure. There can be as many owners as you wish. Just with like any other good. A car is like any other movable good (non real estate) and ownership is nowhere registered. To make things clear make a written contract.
You can use
co-ownership (Miteigentum) Art. 646 - 651a Swiss Civil Code were everyone has a distinct percentage claim (if nothing is stated each has an equal share) or
joint-ownership (Gesamteigentum) Art. 652 - 654a Swiss Civil Code using a
ordinary/simple partnership (Einfache Gesellschaft) Art. 530 - 551 Swiss Code of Obligations. AFAIK the later is simpler in case of disputes and unanimous dissolution.
Please read the linked texts.
But, there can only be one registered holder. The holder does not have to be a owner (See company cars or leased cars). Responsibility of the holder is that the car is only used in roadworthy condition, that the car is only used when insured, and that the car is only used by licensed drivers. Also, the registered holder will have to pay any simple fine (minor speeding ticket, parking fines, etc) were the driver is not known.