Engine cuts off while driving 07 Chevy Impala

07 Impala 3.9 started out stalling while driving and I could
pop her into neutral and she would start back up. Now I
start her drive for however long she decides to kill the
engine power steering gone radio lights dash all that is
bright like a diamond. I go to pop her into neutral and no
way she will not start. You can wait n wait n wait n wait. ...
2 hours I believe is when I came back and she started right
up. Drove her until I got to the light and she killed the
engine and same drill she would not start. Days later I went
and  started her right up and drove her round the block.
Seemed as if she wasn't as powerful as she once was.
Parked her turned her off went to start her up and chug
ching chug she won't turn over. I replaced crankshaft and
camshaft position sensors and all the spark plugs. She still
won't start. Helppp please