Vsc trac, Vsc off and engine light is on and car runs rough

What is your question?

I have a 2004 4 Runner sr5 v6 engine with 156,000 miles on it. All of the sudden my car started running rough when I first turns it on and the Vsc trac, Vsc off and engine light cames on. The roughness stops after about 15 sec. Took it to the dealer Sad they can't tell what's going on only that cyclinder 4 is misfiring. It's not losing pressure or coolant. Any advice on what it can be. I've been seeing items here stating the dealers are quoting the heads need changing, but I refuse to accept that based on what I know so far. The car only runs rough after it has not been running for anwhile and does not give any indication of loss in power Any advice? Thank you in advance.