As Indexes Soar, Does Warren Buffett Know Something Wall Street Doesn't? He Just Made a Move That Could Be a Warning for Investors.

Though indexes slid on Friday, the direction in recent times has been clear. The S&P 500, the Dow Jones Industrial Average and the Nasdaq have been soaring on optimism companies can handle President Donald Trump's tariff plan -- and continue to deliver growth. On top of this, investors have piled into artificial intelligence (AI) stocks amid hopes that these companies will see revenue explode higher as the AI infrastructure buildout scales up. AI behemoth Nvidia has predicted AI infrastructure spending may reach $4 trillion by the end of the decade -- if that happens, many companies and investors could win big.

In fact, momentum has been so strong that the S&P 500 has reached several new records in recent months and is heading for its third consecutive annual gain. Against this bright backdrop, you may be wondering about the latest moves of expert investor Warren Buffett. The billionaire, at the head of Berkshire Hathaway, has delivered a market-beating annual return for shareholders over nearly 60 years, so he's proven his ability to invest through all investment environments -- from bull markets to bear markets and even market crashes.

Now, as indexes soar, Buffett has made a move that could be a warning for investors -- does the Oracle of Omaha, as he's often called, know something Wall Street doesn't? Let's find out.

Image source: The Motley Fool.

Buffett's investment strategy

So, first, a quick note on how Buffett goes about investing. He has built an empire as chairman and chief executive officer of Berkshire Hathaway -- but this isn't due to selecting stocks that take off overnight. Buffett hasn't broadly invested in areas like technology that have seen some stocks soar in the triple- and quadruple-digits in a year or two. Instead, the investor favors industries he knows well and feels comfortable with, and he holds a diversified bunch of stocks in areas including financials, consumer goods, and energy.

Buffett scoops up these players when he feels they're undervalued and have what it takes to gain the recognition of the rest of the market over time -- then he holds on and generally wins as these companies steadily grow earnings and their businesses. He also is a big fan of dividends and has benefited from owning Dividend Kings like Coca-Cola for decades and collecting passive income.

Finally, Buffett doesn't follow market trends and instead sticks to his investment principles throughout market environments. And this leads me to the move Buffett made recently. The billionaire, in the second quarter of this year, was a net seller of stocks for the 11th consecutive quarter -- this means the value of stocks he sold surpasses the value of those he purchased. And this has helped Berkshire Hathaway build a cash position touching record levels this year and settling at $344 billion at the end of the recent quarter.

BRK.B Cash and Short Term Investments (Quarterly) data by YCharts

Here's what Buffett knows

Now, let's consider our question: Does Buffett, showing this sort of caution while others pile into stocks, know something Wall Street doesn't? The investing giant may simply be paying more attention to one key factor, and that's valuation. Though some stocks offer great buying opportunities -- and Buffett has found these and made purchases in recent months, for example, opening a position in UnitedHealth Group and increasing his holding of Pool Corp. -- the overall market is looking pricey. And Buffett, a famous value investor, refuses to buy a stock at just any price.

So, the billionaire likely is focusing on the S&P 500 Shiller CAPE ratio, a metric that shows earnings per share in relation to price over a 10-year period -- and he probably doesn't like what he sees. The metric this year reached a level that it's only seen two other times in the past, signaling the overall market is pricey.

S&P 500 Shiller CAPE Ratio data by YCharts

During times like these, it's not surprising that Buffett isn't deploying boatloads of cash and instead chooses to lock in profits on some stocks and invest cautiously.

What does this mean for you as an investor? This doesn't suggest you should unload your stocks and stop investing. Instead, it means that, like Buffett, you should look for opportunities -- as they exist in every market phase -- and at the same time, set aside some cash that you might deploy in the future too. After all, certain players that look expensive today may trade for more reasonable prices at some point down the road -- and, like Buffett, you'll want to be ready to seize the opportunity, hold on, and score a win over the long run.

Adria Cimino has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Berkshire Hathaway and Nvidia. The Motley Fool recommends UnitedHealth Group. The Motley Fool has a disclosure policy.