[almostkorean]

I think automatically is not the best term here. I'm not an expert, but there are borrowing and lending protocols that let you borrow a large amount of their token pool as long as it is paid back within the same block (plus some fee). So you can write a script to run a transaction that:

  1. borrows a large amount of money
  2. use the large amount of money to do arbitrage
  3. pays back the large amount of money plus any fees
  4. keep profits

and it does so "atomically", so if you can't repay the loan then the transaction fails and the whole thing never happened. or you could lose money if the transaction is successful but the trade is not profitable.

like I said, I'm not an expert so someone correct me if I'm wrong