Well now,, that is another question! Or two!! Possible spark plug, coil on spark plug, injector or wiring problem , vacuum leak etc... it needs to be tested by a mechanic so no money is wasted on parts you dont need.
If you smell fuel (like a flooded engine) DO NOT drive it! Flashing light usually signals an injector problem. It could be as stated by the other's a spark, coil, wire type of problem., but all I'm saying,if you smell fuel, don't drive it.
I just had the same problem with my 2001 town car. Misfire cylinder 5 and when I pulled the coil off the plug it was full of engine coolant. I dried the coil boot and spring and changed the plug ( whoever did plugs last was smart enough to use never sieze on them) misfire is gone. I then added leak repair to radiator for gasket repair in case there is a coolant leak. Cost me $17.00 for the total repair but that was doing it myself, it's actually quite easy it took me about twenty minutes. Good luck.
Just wanted to add to the list, have similar problems with car jerking when it gets to about 40-50 mph. Also the check engine light flickers. I have a 2005 Lincoln Navigator and took it to a ford dealer. Bad coils 5 and 6 that I had to replace.
I had a similar problem but the coils and computer checked out....I finally found out a common problem that causes the NAV (and similar F-150 trucks) to run this way is a vacuum leak on the "boot" that connects to the PCV valve on the passenger side bank, valve cover. The hole is normally under the metal routing connector, so it's hard to hear or seen...and in my case was intermintant, based on temp. I was getting nearly every lean fuel/catalytic converter/EGR valve error code....it was a pain in the butt to track down the issue. The thing that caught my attention was your comment about the flashing "engine light"...in the NAV at least, this means that the issue is serious, I guess it's trying to say..."Ya see the light....hey you, driver, do you see the light....are you REALLY just going to keep driving....LOOK AT THE FU$&ING LIGHT!!!" The SUV does have a good point, if you let the fuel trim run on lean side and cause the computer to increase the ratio to compensate, it will burn out $3,000 (cost...not installed or retailed) worth of catalytic converters...and they are hard to find if you have the 4X4.