Can an insurance company confiscate your car without your consent?

No they cannot... Unless... the vehicle was totalled in an accident and they have paid you for the actual cash value. They'll still require you sign certain documents releasing the vehicle to them for salvage value.

Or... is your insurance company also your leinholder? Many insurance companies are now in the lending business. If that's the case, and you didn't make the payments then, of course, they can reposess the vehicle - it's legally theirs anyway until the loan is paid-off.