* ADP and ISM non-manufacturing data on tap
* Many investors worry about low volume and volatility
* Protective Life jumps in premarket, Dai-ichi to buy
* Dow up 4 pts, S&P down 1.9 pt, Nasdaq down 4.75 pts
By Ryan Vlastelica
NEW YORK, June 4 (Reuters) - U.S. stock index futures mostly edged lower on Wednesday as investors refrained from making large bets, with indexes near record levels, ahead of data on the labor market and services sector.
* Equities have been strong lately, with the S&P 500 up for seven of the past nine sessions, hitting multiple records over that period. However, the gains have come in anemic trading volume, suggesting the rally lacks conviction.
* Trading catalysts could come with the 8:15 a.m. (1215 GMT) release of ADP's May data on private sector employment, which is expected to show 210,000 jobs added last month, fewer than in April. After the market opens, the Institute for Supply Management's May read on services will be released; analysts expect it to rise by 0.3 to 55.5.
* Recent data has pointed to economic improvements, raising hopes for the May jobs report, which will be released on Friday. Analysts expect 218,000 jobs to have been added in May.
* S&P 500 futures fell 1.9 point and were below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures rose 4 points and Nasdaq 100 futures lost 4.75 points.
* Roughly 84,500 S&P 500 e-mini contracts traded as of 7:00 a.m., suggesting another light day of trading. On Tuesday, the SPDR S&P 500 ETF, typically one of the most heavily traded securities on a given day, had one of its most thinly traded sessions of 2014.
* Along with volume, volatility has been light, despite a 4.1 percent pop in the CBOE Volatility index over the past two sessions. The "fear index" remains below 12, well below the historical average of 20, which has some investors concerned the market has become complacent.
* Market action is expected to spike on Thursday, when the European Central Bank meets. Many investors expect bold action by the bank to fight low inflation and high unemployment.
* In company news, Protective Life jumped 18 percent to $69.55 in heavy premarket trading after Japan's Dai-ichi Life Insurance Co agreed to buy the company for $5.7 billion.
* The Wall Street Journal reported that NRG Energy Inc is close to a deal worth more than $800 million to buy Alta Wind Energy Center, the largest wind farm in North America.
* Financial information service provider Markit Ltd IPO-MRKT.O said it expected its initial public offering to be priced at $23-$25 per share, which could value the company at up to $4.47 billion. (Editing by Bernadette Baum)