Not yet but I wouldn't be surprised if that will be a reality in the future. Actually it already IS A REALITY in the United States. look up civil asset forfeiture.
Retarded cop can stop you, search your car, find you have some money and if he (using his brain process) suspects the money may be of illegal origin, he can seize it. Then you can spend a year or more arguing in courts and perhaps you will get it︀ back.
It is not yet applied with car stops now in Europe but such things︁ actually happen in airports (well, happened before coronavirus lockdown). If you carry over 10K through︂ an airport and you're searched, you will be stopped, accused of something (such as funding︃ terrorists) and you will be fined 5-10 % of the amount you carry as a︄ sort of blackmail if you want to continue to your destination. I'm not kidding, this︅ is regularly happening in Netherlands, Belgium and other countries.