1987 Chevy Camaro engine wont stay running once in a while

Hi,

My IROC Z28 has a problem when I turn the motor off for a few moments like when I run into a store to pick something up. When I come out the car won't regulate and idle, it just dies. It should regulate at 700 rpm's. But it is like the regulator isn't working. I have to sit there and turn the engine key off and on and start the car as much as 20 times before the car starts to regulate normally. Is there something like a motor that controls the idle or is it just the gas being altered by the computer that regulates it. I love this car and would really like to solve this problem.

Thanks much
Ernie