It's normal. I have been having a 96 4 Runner for 10 years now and I've always had that noise. Someone explained what it was to me but I don't remember.
I have a 1996 4 Runner that I bought new and it developed that same "clicking under the seat" problem (mine was the drivers seat only, and your description fit my problem to the tee). It was driving me crazy and I am sure since your 4 Runner is so new it is really giving you fits.
My...
