ETH pre-merge – anything to do given POW fork?

So I’ve read a few times that there will be a POW fork after the merge. I’ve also read that there may be an issue with POW in relation to the new POS where moving around (presumably to sell on an exchange) may cause an issue with the POS tokens (I forget the name of the issue…?read back or something?) and that this could cause loss of the new POS tokens.

I have seen some people suggest to temporarily transfer current ETH holdings to a new wallet ahead of the merge in order to mitigate this risk. Can someone here please help me understand what the issue is and if there is actually something wise to do ahead of time or if it can just be dealt with later on?

Much appreciated.