If you had a medical issue that may cause a waiver, it is good to bring the records with you from a POV of defending why it isn't a medical issue currently. I.E. a doc when you were 9 and had allergies may have said it was asthma. That will cause issues. However, if you can prove that it was ragweed and never used an inhaler, it will be beneficial to you.
If you have had no medical issues, don't worry. You just fill out the forms and move on from there. Be honest and open, because if you try to hide it, they will find it. DodMERB exams are not like sports physicals where they weigh you, look in your ears, throat and nose, ask a few questions, and call you clear to go. It is what the military calls a "long physical", and they check everything from your eyes to your toes and everywhere in between.
If you are military, they will give you a DodMERB doc that traditionally is off base. You can contact them and ask to go to your military doc on base. It is a 30 second phone call. It also makes it easier because they have all of your medical records to begin with.