2000 Buick Century hard start/stalling

Mom in law has a 2000 buick century. Recently its been having a real hard time starting and will occasionally stall out a stop light.

No matter what, it takes 3 & 4 tries to start it.

I have only recently started doing the maintenance for her, but the plugs and wires were recently replaced (they were due).

There are no problem codes on the computer.

However, I didn't do the fuel filter - and at 41K I guess that is also due.

Any other idea's

Thanks

Andrew