1994 Volvo 850 Car stalls during normal driving

The engine is actually a 5 cyl. (Fyi)
While driving the engine will stall. If we wait 10-20 seconds, then restart, it will start up just fine and continue to run o.K. The frequency of this happening has gone from once every 3-4 months down to daily (which is where we are at now). One event that happened recently was the car lunged forward as if if briefly stomping on the accellerator. Otherwise, the car starts fine and runs good.