Investors may want to take some money off the table when the market has up days, according to a technical strategist. BTIG's Jonathan Krinsky said in a note to clients Sunday that the S & P 500 is running into resistance around the 4,000 level and will have trouble building on gains from here. The broad market index briefly traded above that level on Friday before closing at 3,961.63. "The SPX got up to 4,012 on Friday, a few points shy of the unfilled gap at 4,017, and ~10% off recent lows. Our view remains that it's prudent to reduce risk above 4,000 as we are still in the confines of a bear market," Krinsky wrote. "While we saw the most amount of 4-week highs since March, the paradox here is that the last two times we saw this amount of 4-week highs it signaled an exhaustion of the rally." The S & P 500 gained more than 2.5% last week, its second positive week in three, and Wall Street traders are trying to determine if the market has already bottomed near 3,667 on June 16. While the recent uptrend has eased investor fears, there are still reasons to be skeptical of the rally, including a lack of breakout moves among individual stocks. Krinsky wrote that he "would like to see 52-week highs expand to signify a more durable rally." Similarly, MKM chief market technician JC O'Hara said in a note Sunday that the "psychological round number of 4,000" seemed to be a road bump for stocks, but said 4,200 was the "key line in the sand." Wolfe Research strategist Rob Ginsberg wrote that stocks could be trading around the 4,000 level for the next few weeks. "The Bears need to break 3919 to regain near-term control, if not, a grind higher towards 4150/4200 over the next few weeks wouldn't surprise us," Ginsberg wrote. The S & P 500 last closed above 4,000 on June 9. — CNBC's Michael Bloom contributed to this report.