First, look at center console security light w/key in IG SW.
Second, check battery & alternator connection.
Third read codes.
I just saw two this week, where engine just shut down while driving.
Was not bad battery.
Was not a loose battery connection. Very common just after battery replaced.
Was not bad alternator, or wire lug or plug
Was not bad fuel pump.
Was not fuel cut-off switch tripped.
Was not crank sensor wire cut (improper routing) while rubbing on fan belt.
Vehicle 1 98LC) Immobilizer. Noted by security light flashing, with key in IG. EFI fuse prongs looked a bit burnt. Replaced fuse, started. Will need new fuse box or EFI jumper.
Vehicle 2 98LC) MAF. Found DTC, with code reader for both MAF and Immobilizer. Tapped on MAF engine shut down (repeatable). Replaced MAF (OEM), no issues since. Watching immobilizer for further issues!