Investors should pay attention to the actions of the legendary investor.Warren Buffett is telling investors something -- not through what he has said, but through his actions with the balance sheet of his investment conglomerate Berkshire Hathaway (BRK.A -0.40%) (BRK.B 0.83%). These actions should be taken as a warning sign with the stock market reaching elevated valuation levels in recent months.As the market and Berkshire Hathaway stock soar, Buffett is pulling back and building a huge cash position. Shou ...