At 12.30pm, the key index was down 2.95 points to 1,598.47 with investors unwilling to stray far from the 1,600 psychological level.
Among the blue chips, investors took money off IHH, which slipped nine sen to RM5.32, Digi down nine sen to RM3.69 and Top Glove falling 10 sen to RM5.05.
Hartalega was also down 16 sen to RM9.38 while Axiata dipped three sen to RM3.65.
Amid news that the ship blocking the Suez Canal would soon be refloated, investors are proving jittery over oil prices.
Brent crude slipped 99 cents or RM1.5% to US$63.58 a barrel, leading to some retreat in energy counters.
Bursa Malaysia's Energy Index dropped 1% as investors awaited more developments.
Oil and gas counter Deleum however was seen plunging 6.5 sen to 10.4% to 56 sen on news that Petronas had suspended its 60%-owned subsidiary, Deleum Primera, from participating in the national oil company's tenders and contracts until further notice.
Seeing strong trading interest, Berjaya Corp topped the day's trading volume with 303.65 million shares traded. The conglomerate was up two sen to 32.5 sen amid continued optimism over recent developments in its management and shareholding.
Other top actives wee Macpie down 10.5 sen to 36 sen and Widad rising seven sen to 62.5 sen.
Meanwhile, Asian equities were mostly positive as US President Joe Biden was due to outline his infrastructure spending plans this week.
In Japan, the Nikkei was up 1.2% while South Korea's Kospi rose 0.2%.
China's composite index gained 0.8% and Hong Kong's Hang Seng was up 0.3%.
In Australia, the ASX200 dropped 0.2%.