2000 nissan sentra just had new catalytic converters replaced is still shutting down while driving

I wouldn't think the catalytic converters would have anything to do w/ that. What it sounds like is that the engine isn't getting fuel. You may need a tune up, it may need new fuel lines, there may be trash in the fuel pump/fuel line or anywhere fuel flows. That also may mean you need a new head gasket, but I'm not certain on that. The only way the converter could be involved is if your engine isn't burning all the fuel in the cylinder and it is exiting through the exhaust, getting in the converter (which will stop some of it), and then eating away at the converter. What I'd to is take it to a shop (if you can get it there), have a mechanic ride w/ you and try to replicate this problem. He or she then could really narrow it down for you and tell you what it is and how much it will cost.