My car runs fine cut it off and it is slow to crank or will not crank on 1999 Pontiac Grand Am

I can go to wal-mart and my car starts fine when i leave i can go to another store but maybe only be there for 5 minutes and my car slowly cranks or wont start have replaced top of motor radiotor and the fuel pump and battery what can it be

Asked by for the 1999 Pontiac Grand Am
2 answers
Your car does not like for you to shop any store but wal-mart!

My guess is you have a starter motor problem.
I agree with wetry but you did not say how you got it going if it starts with a boost then check charging system