Attention, Investors: Now Is The Time To Start Panicking

"Dow 20K" has come and gone, and the index is one strong day away from hitting the 21,000 mark. But this doesn't mean it is clear sailing ahead. The opposite may be true.

According to a Bloomberg report, there are plenty of signs behind the scenes that there has been a shift in investor sentiment — and not necessarily for the better. For instance, companies with revenue bases less sensitive to economic growth — such as health care and utilities — have outperformed over the past few weeks. This marks a reversal from the prior months when financial stocks led the rally.

And if this doesn't serve as a clear enough sign that investors are concerned, consider the rising demand for Volatility Index products. Specifically, net positions in VIX futures, commonly referred to as the "fear index," rose in three of the past four weeks even though it is sitting near record low levels and around 25 percent below its five-year historical average.

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Bloomberg noted the shift in investor sentiment is coming at a key point in President Donald Trump's administration where he now needs to make good on various promises such as tax reform and infrastructure spending. Trump will also be addressing Congress Tuesday, and investors will be looking for any sign of progress or the "Trump rally" could come to a halt.

"President Trump's speech on Tuesday needs to get specific because this market has risen on expectations, which have yet to crystallize," Tom Siomades, head of Hartford Funds Investment Consulting Group, told Bloomberg. "If it is obscure or has little clarity, you could begin to see the market get more cautious."