Doll said Syria, the lack of clarity on the Fed's plans for tapering back its $85 billion bond purchase program, and uncertainty over whether former Treasury Secretary Larry Summers or Fed Vice Chair Janet Yellen will replace Fed Chairman Ben Bernanke in January are among the issues weighing on markets.
"It's the collection of these uncertainties and the absence of revenues and earnings that puts us in this funk," Doll said, adding selling could continue in September. "But I don't see big downside."
Angst about Syria
Anxiety about Syria was tempered slightly over the weekend, after PresidentBarack Obama said he would ask Congress to approve a military strike on the country. Traders had been expecting the U.S. to go it alone against Syria with a limited, strategic missile strike as early as this weekend, after the British Parliament voted Thursday against getting involved. Now, Congress will return to consider action Sept. 9.
"Frankly, at the end of the day it's another complicating factor in the midst of many," said Mark Luschini, chief investment strategist at Janney Montgomery.
Deutsche Bank's Alan Ruskin said there should be an initial bid in the dollar if there is an assault by the U.S. "There is a bit of uncertainty. You might get some minor flight to quality that doesn't last very long," said Ruskin, head of G-10 foreign exchange strategy. But markets would have a much more serious, longer term reaction if other countries become involved, such as Syrian ally Iran, or if there is an attack on Israel.
Stocks, trading hesitantly into the long Labor Day weekend, could trade fairly quietly ahead of the jobs report. "I think people are going to just sit on their hands," said Janney's Luschini.
Geopolitics will stay in the forefront as President Obama heads to the G-20 in Russia, a country whose leadership has been outspoken against U.S. intervention on Syria. The G-20 gathers Thursday, and the president is expected to leave Washington Tuesday, which stirred some speculation in markets that a military strike could come against Syria as soon as this weekend.
Nervousness about Syria showed up in Friday's trading, and the Dow finished lower by 30 points ahead of the three-day weekend. As Secretary of State John Kerry spoke Friday, laying out the case against the Syrian government and the U.S. response,stocks moved to their lows of the day and then erased those losses while he was speaking.
"Starting off the speech, it was clear he was making a case for going forward with some sort of military campaign, and toward the end you understood it was something that's going to be done remotely with a shot across the bow effect rather than something lengthy with troops involved. If it's brief, I think that is good for the markets, but time will tell once something does begin, what the response will be then," said
Oil has so far been the most volatile market when it comes to Syria. West Texas Intermediate crude finished Friday at $107.65 per barrel, after hitting a two-year high of $112.24 per barrel Wednesday. Electronic trading in U.S. energy futures resumes Sunday at 6 p.m. ET and continues until Monday at 1:15 p.m.
The Fed is expected by many economists to announce plans to reduce bond purchases, or quantitative easing, if Friday's jobs number is strong or mostly in line number with expectations.
Economists expect to see 180,000 nonfarm payrolls were added in August, and the unemployment rate unchanged at 7.4 percent, according to Reuters Thompson. There were 162,000 jobs added in July.
"If the number disappoints then the guessing game will remain alive and well until the Fed meets in the middle of the month," Luschini said.
David Ader, chief Treasury strategist at CRT Capital, said he expects the Fed to decide to taper at its September meeting — no matter what.
"I don't think the unemployment number is going to matter. I don't think it's going to change what the Fed is going to do. I think tapering is going to be done," he said.
Of course, traders will immediately begin to speculate on the magnitude of the Fed's gradual tapering as soon as the number is reported. Estimates for the first round of tapering range from about $10 billion to $25 billion.
(Read more: What everyone gets wrong about monetary policy)
Besides the jobs number, there is a large amount of data that traders will be watching both with the Fed in mind and to see how the economy is faring this quarter. The third quarter seems to be lagging the second quarter's 2.5-percent growth rate, even though many economists had been expecting it to be stronger.
ISM manufacturing data is reported Tuesday, auto sales are Wednesday, and ADP private sector payroll data is Thursday. There are also Fed speakers next week, including San Francisco Fed President John Williams Tuesday, and hawkish dissenter Kansas City Fed President Esther George speaks on Friday.
What to Watch
Labor Day holiday
0858 am Manufacturing PMI
1000 am ISM manufacturing
1000 am Construction spending
1230 pm San Francisco Fed President John Williams
August vehicle sales
0700 am Mortgage applications
0830 am International trade
0200 pm Beige book
0800 pm Minneapolis Fed President Narayana Kocherlakota
August chain store sales
0815 am ADP employment
0830 am Initial claims
0830 am Productivity and costs
0900 am Minneapolis Fed's Kocherlakota
1000 am ISM nonmanufacturing
1000 am Factory orders
0800 am Chicago Fed President Charles Evans
0830 am Employment report
1330 pm Kansas City Fed President Esther George
—By CNBC's Patti Domm. Follow here on Twitter