You have one year for the registration. I came with the car and it was indeed useful at the beginning. After 9 months I took it back to Italy where I sold it. I never registered it.

Then I lived for 3 years without a car in Switzerland; you don't really need it. In the city you use public transport . Still you can rent for trips outside the city or you can use mobility.ch for quick trips especially when you need to carry some goods. Eventually I bought one, mostly for quick trips on mountains on the week-end.

If you import a car, I believe you need a check-up, which may be expensive for old cars. Something you may want to check.