Power Locks problem in '98 Chevy Lumina

[ys1966]

I have a '98 Chevy Lumina.
the problem is with the power locks and I don't have keyless entry.
when I drive the car alone, after I park and turn off the car then I am able to lock the car from driver side. But I can do it only once, that means, if I unlock the car and try to lock again it does not work.
when I drive the car with passenger and after parking and turn off, both of us open the doors, power locks don't work from either side.
I have to wait a little bit or close the doors or start the car before I can use the power lock and sometimes this even does not help.