I call that tarot-overload..
I did a Reflecting Pools spread one day (30-card-spread), and slept great the night that followed dreaming in full color and felt fabulous when I woke up.
The next day I did another one and the second night was not as pleasant.. Tossing, turning, finding it hard to relax and the third-eye-strain (slight headache right in the middle of my forehead) felt horrible.
So, too much tarot or not enough cleansing inbetween I guess..
Cleansing, grounding and shielding would be the way to go, or back down from the number of readings (if possible) and work ones way up bit by bit.
For some, drinking a glass of water (and having another glass of water - not for drinking but for soaking up the extra energy) on the table helps.
Also, washing ones hands (and face?) could be worth a try to clear the energy between readings.
Maybe a glass or bowl of saltwater on the table could help soak up the extra energy and/or help clear you between readings. Washing your hands with salt could be worth a try considering the cleansing qualities of salt..
Just a few ideas...
The main thing would be to find a way to clear the energy after a reading, and shielding could also help you along.