Engine Mechanical problem
1998 Mercedes Benz S600 V12 Two Wheel Drive Automatic 106000 miles

i did a tune up, it was throwing a code for missfire and o2 sensers. at that time i changed the plug wires the computer called for and all plugs, i changed the 2 o2 sensers before the cat and all codes reset. shortly after it started to run with a loss of power and i changed the fule filter and it reset and ran fine. it stiil runs very well but on acation after it is hot and i go to restart it spins the ingine longer than ussall to restart. and from cold to warm up sometimes it will serge real quick when i step on the gas like i am pushing on the throddle and it does not respond and suddenly it comes on and wont do it again till i restart or till its cold. it dose not trip a code, i am wondering if because i did not change a couple of the wires and the 2 back o2 sensers if that may be the problem.