When you apply for credit, most creditors report the application to one or more credit bureaus, and that’s called an “inquiry”. Any more than a few inquiries per year hurts your credit score a little. A bunch of inquiries can hurt your score a lot.
With new credit score procedures, applying for a string or auto or home loans in a row will only count as one inquiry (within about two weeks of each other) so the damage is a lot less now than before.
Getting inquiries deleted is a bear, and goes well beyond the cope of this lofty tome.
Otherwise, waiting a few months allows those inquiries to age and their impact on the score drops away.