Hello,
From what I read, someone who sells btc sometimes has trouble receiving the fiats in its bank account. If the sum is large, the bank turns on all its red lights. I guess it's not a problem for someone famous, but for an ordinary citizen, how it happens if he lives modestly, recovers his private keys that he lost 10 years ago and finds himself with millions?
It won't be a problem if the bitcoins are his because the government has nothing against him as long as the bitcoins are yours. But the problem here is the envy you will face because once there are people who know about the massive amount of bitcoins you have, most of them will be interested in getting it from you, and you won't get away with it once they know your location. That's why the best thing to do is to lay low and chill, and you just need to learn the basics on how to hide your identity when converting it to fiat to protect yourself from those kinds of guys and also from huge numbers of questions from the banks.