I used my wife's car today,99 E320 and,to my surprise,it did not crank this morning,turned the key and heard the click from the starter and the rpm gage went all the way up and down,no start,tried it 3 times,third time started right up,starter might get tired?,or electronic key...?

check your battery connections under the rear seat. It might be time for a new battery?
Dustin