2006 nissan altima

check your fuel pressure should be 52 psi If that checks out your crank or cam sensors may
be going bad. if this is the case Nissan recommends changing both sensors

Agreed, start with any check engine lights you might have, if you don’t have any the next step would be to find what is missing when the car stalls, you may be able to hook up a fuel pressure gauge and tape it to the windshield that way you can see if the fuel pressure drops off before it stalls if it stays constant it could indicate an ignition problem or a problem with the ignition switch itself. To check the ignition switch you might try wiggling the key while the engine is running, if the engine stalls or stumbles you might look to the ignition switch circuit for the cause.