2006 Buick Lesabre

MAny possiblilities.

May be a wiring issue. While at idle, a wiggle t4est can be performed on suspect wiring harnesses.

If you can hook up a scanner that is capable of freeze frame data, a snapshot can be taken of the data stream to see if it yeilds useable data of what may be happening.

IF this is more common going uphill, I would question the fuel pump. Use a pressure gauge to determine if the pressure is out of spec. If not drive it with the gauge hooked up and see if the pressure drops off during the stall.

IF this is more common when engine is hot and does not want to start right back up an ignition module may be suspect. Use a hair dryer to heat it up when its cold to see it you can create the no start.