2004 Saturn L300-Stalling problems

Recently my car has stalled on me when I’ve stopped at stop lights. The radio stays on, but I think it’s just the engine that turns off. I have to turn the car compleltly off and then on again. It sometimes takes a few tries, but it does turn on again and I am able to drive it again. I have taken it to a repair shop twice now and both times they’ve said they cant replicate the problem and cant seem to figure out whats wrong. They have scanned my car and I was told they didnt get any codes telling them of the problem. Any ideas as to what the issue could be?

How many miles are on it? What is the state of things in terms of maintenance? Age of spark plugs? Wires? Filters? When it doesn’t stall how does it idle? Smooth? Rough & vibrating? Does it stall nice & quietly, or does it seem to sort of jump & lurch a little & stall?

My top guesses offhand with only the info I have would be a faulty idle air control (IAC) valve or circuit or a torque converter clutch problem.