If you make all your credit applications for car loans within a two-week period, the FICO score is supposed to count them as a single inquiry. Shopping for the best rates is encouraged. However, if you apply for a car loan once a month, each application will count as a separate inquiry. The same is true for mortgage applications.
10% of your FICO score is determined by "new credit." If you are suddenly making lots of applications for credit, lenders worry that you are in some kind of trouble. Or they think that creditors are denying you credit for some good reason, and you have to keep applying. That's why a lot of inquiries can drag your score down.
I made a major purchase on a new card and it really took me a minute to stop and think hey that's it for cards for hrre months while I pay off this 0 percent.