turns over but wont start

when it first started doing it as long as it was a warm day i could put gas in it
and it would start up and for the rest of that day it would start up on its own
until the next day somedays it wouldnt start at all i put new plugs in it and
bought 3 new wires it has 4 but the 2 wih coils i was told as long as they
spark when u turn it over then there fine but now it just turns over wont run at
all 1997 c230 Mercedes benz