NEW YORK (TheStreet) -- Tuesday was one helluva turbulent trading session as benchmark indexes rallied above 1%, crashed deep into the red by the afternoon and ended the day little changed.

The day's jittery movements were par for the course for a market that has whipsawed from rallies to selloffs so far this year.

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Some analysts trace increasing volatility back to uncertainty over exactly what the Federal Reserve will do this year.

"The Fed [is] on the verge of going from an easing cycle to something tighter ... less easy," said Wells Fargo's Scott Wren in a call. Volatility is common "any time you're typically in that transition and you're unsure of the pace of the Fed's moves, you're uncertain as to when the timing's going to start."

The S&P 500 fell 0.26%, the Dow Jones Industrial Average dropped 0.15% and the Nasdaq slipped 0.07%.

Oil was again one of the main determinants of market direction with a midday return to six-year lows freaking markets.

"Oil hit a tailspin again this afternoon and that's what's taken equities down. It's a case of the markets worrying about deflation now and what impact that could have on the global recovery," said Chris Gaffney, senior market strategist for EverBank Wealth Management, in a call.

West Texas Intermediate fell overnight after the United Arab Emirates reiterated it will not reduce production in the face of global oversupply and faltering demand from key regions including China and Europe.

"The strategy will not change," said UAE Oil Minister Suhail bin Mohammed al-Mazroui. "We are telling the market and other producers that they need to be rational." OPEC has been reluctant to cut output lest the member countries lose market share. OPEC will gather in June for its next scheduled meeting.

WTI recovered to trade at $46.27 a barrel, bouncing back from losses of more than 3% earlier Tuesday. Since last summer, oil prices have dropped nearly 60%.

"The volatility, I think, is a market trying to figure out what the dominant theme in 2015 is going to be," added David Bechtel, principal at Barrow Funds. On the one hand, there's the possibility of a delayed rate hike on global economic sluggishness, he said, but "another one is oil has been cut in half (from $110 to $50) and people are still calculating the consequences."

Amazon(AMZN) - Get Report shares were up 1.1% on an upgrade to "buy" from Citigroup. "We believe Amazon's valuation represents a good risk/reward as we see valuation support near $300 and upside to at least $354 without assuming multiple expansion," analysts said.

Apple(AAPL) - Get Report was also higher after Credit Suisse upgraded the stock to "outperform" and upped its price target. The firm said the revision was based on "sustainable iPhone volume base" and earnings momentum. Separately, a patent filed by Apple was published in which the company detailed plans to develop a sports camera system controlled by phone or watch. GoPro(GPRO) - Get Report , which creates durable cameras, tumbled more than 12%.

MetLife(MET) - Get Report was 1.3% on news the largest life insurer in the U.S. will file a lawsuit against federal regulators in a challenge to their "too-big-to-fail" designation. The company said the tougher oversight would make its offerings more expensive with little benefit to its fiscal stability.

Philips(PHG) - Get Report fell 1.9% following a warning that full-year earnings will be reduced by about 225 million euros. The Netherlands-based medical equipment company said the hit was due to legal charges and the impact of foreign exchange.

RadioShack (RSH) was more than 19% higher after receiving a financing offer from Salus Capital. The $500 million offer expires Thursday.

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--Written by Keris Alison Lahiff in New York.