"In this sort of environment where the news is mixed and the valuations are pretty full, it's an ample time for uncertainties to come to the fore," said Bruce McCain, chief investment strategist at Key Private Bank.
The major indexes turned lower as the close neared. The Dow Jones industrial average was about 8 points lower after earlier adding more than 150 points.
Materials and financials led S&P 500 advancers while telecommunications and health care were among the greatest decliners. The iShares Nasdaq Biotechnology ETF (IBB) traded more than 1.5 percent lower in afternoon trade.
"I just think we jumped out of the gate a little ahead of ourselves with Europe and China this morning," said Peter Coleman, head trader at Convergex.
The Shanghai composite jumped more than 1.6 percent amid some encouraging inflation data.
The Japanese yen reversed in late-morning trade to resume strengthening against the U.S. dollar, near 107.9 yen as of 3:36 p.m. ET.
"The yen is still hanging tough. It's a flight-to-safety currency and perhaps you have a little bit of, the belief system in central banks is breaking down," said John Caruso, senior market strategist at RJO Futures.
Gold futures for June delivery jumped $14.20 to $1,258.00 an ounce.
U.S. crude oil futures settled up 64 cents, or 1.61 percent, at $40.36 a barrel. Earlier, WTI hit its highest since March 23.
Read MoreLots to rock the market in the week ahead
The U.S .dollar index held slightly lower, with the euro above $1.14.
"If we put a low in oil and a top in the dollar in the short-term, that's very constructive for corporate America," said Art Hogan, chief market strategist at Wunderlich Securities.
No major U.S. data is due Monday. Retail sales and inflation data are expected later in the week.
Treasury yields came off highs, with the 2-year yield near 0.70 percent and 10-year yield around 1.73 percent as of 2:34 p.m. ET.
The Dow transports held about 0.2 percent higher after briefly rising more than 1 percent higher to top its 200-day moving average in intraday trade.
U.S. President Barack Obama is happy with the job done by Federal Reserve Chair Janet Yellen, with whom he is meeting on Monday to discuss regulatory issues and world economy, the White House said in a Reuters report.
"The president has been pleased with the way she has fulfilled what is a critically important job," White House spokesman Josh Earnest said at a news briefing.
In prepared remarks for a Monday morning speech, New York Federal Reserve Bank President William Dudley focused on the links between economic and geographic mobility in the United States and did not comment on monetary policy or the economy, Reuters said.
Alcoa is set to unofficially kick off the first-quarter reporting season with its earnings after the close, while major banks such as JPMorgan Chase, Bank of America and Citigroup are all due to post results later in the week.
"I think the focus this week will be on earnings. The challenge will be, can investors stomach current valuations?" said Jack Ablin, chief investment officer at BMO Private Bank.
Aggregate first-quarter S&P 500 earnings are estimated at $26.17, representing a decline of 8.1 percent year-over-year, for the third quarterly decline in a row, according to a Friday note from Lindsey Bell, senior analyst at S&P Global Market Intelligence. "Such a steep decline in growth hasn't been recorded since second-quarter 2009," she said.
U.S. stock index futures held higher ahead of the open, with Dow futures up about 70 points.
"Perhaps investors anticipate this is going to be the worst quarter of the year and maybe brighter skies ahead," Ablin said.
Asian stocks closed mixed overnight, with the Nikkei 225 falling 0.44 percent while the Shanghai composite gained more than 1.6 percent.
China's producer prices declined a less-than-expected 4.3 percent in March from a year earlier while consumer prices were unchanged from February's rate with a 2.3 percent rise last month.
U.S. stocks closed well off session highs Friday, despite a rally in oil, as the yen strengthened against the U.S. dollar.
The major averages declined more than 1 percent for the week, the worst since Feb. 5 for S&P 500 and Nasdaq composite and the worst since Feb. 12 for the Dow Jones industrial average.
Read More Early movers: NSC, YHOO, HTS, GOOGL, OSTK, GE, BLMN, QSR, GM & more
In afternoon trade, the Dow Jones industrial average added 91 points, or 0.52 percent, to 17,668, with Goldman Sachs leading advancers and Nike the greatest laggard.
The S&P 500 gained 8 points, or 0.4 percent, to 2,055, with materials leading six sectors higher and telecommunications the greatest decliner.
The Nasdaq composite rose 23 points, or 0.25 percent, to 4,874.
The CBOE Volatility Index (VIX), widely considered the best gauge of fear in the market, rose to trade near 15.25.
About three stocks advanced for every decliner on the New York Stock Exchange, with an exchange volume of 396 million and a composite volume of 1.8 billion in afternoon trade.
U.S. crude oil futures for May delivery gained 54 cents to $40.28 a barrel on the New York Mercantile Exchange.
Gold futures for June delivery gained $15.70 to $1,259.50 an ounce as of 1:08 p.m. ET.
—Reuters contributed to this report.
Earnings: Alcoa, Pep Boys
Earnings: Fastenal, CSX, Adtran
6 a.m. NFIB survey
8:30 a.m. Import prices
9 a.m. Philadelphia Fed President Patrick Harker
1 p.m. $24 billion three-year note auction
2 p.m. Federal budget
3 p.m. San Francisco Fed President John Williams
4 p.m. Richmond Fed President Jeffrey Lacker
Earnings: JPMorgan Chase, Commerce Bancshares, Pier 1 Imports, Kinder Morgan, Noble
8:30 a.m. Retail sales; PPI
10 a.m. Business inventories
10:30 a.m. EIA oil inventories
1 p.m. $20 billion 10-year note auction
2 p.m. Beige book
Earnings: Bank of America, BlackRock, Wells Fargo, PNC Financial, First Republic Bank, Freeport-McMoRan, Snap-on, Advanced Micro, Delta Air Lines, Shaw Communications, Infosys
8 a.m. Bank of Japan Governor Haruhiko Kuroda at CFR, New York
8:30 a.m. Jobless claims
8:30 a.m. CPI
10 a.m. Atlanta Fed President Dennis Lockhart
10 a.m. Fed Gov. Jerome Powell at Senate Banking subcommittee
1 p.m. $12 billion 30-year bond auction
Earnings: Citigroup, Charles Schwab
8:30 a.m. Empire State survey
9:15 a.m. Industrial production
10 a.m. Consumer sentiment
12:50 p.m. Chicago Fed President Charles Evans
4 p.m. Feb TIC data
*Planner subject to change.
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