2011 SES Rough Start

[greenhorn]

Hello, new here with a problem I've been having on and off for a few months on my manual fiesta with 135k miles. Sometime over the winter my fiesta would occasionally start rough, like it was struggling to get going, with the revs bouncing below 1000 and slowly working their way up to a even, normal idle. The TCS off warning lights would turn on on the dash. Usually if I turned it off and back on, it would start normal the second or third time with no TCS off warning. Occasionally the check engine light would come on, but not always. Eventually I got a code reader and it was the code for cylinder 4 misfire. Replaced the spark plugs, wires, and ignition coil, none of these helped. Had a radiator leak repaired with a new radiator. Lately the check engine light doesn't come on at all, but the start is rougher though if I let it get to normal idle it starts normal the second time. When I start the car in the garage I can smell sweet and the coolant seems to be very slowly dropping, but no evident leak on the garage floor since the radiator replacement. I've taken the car to the shop once, but it never had the issue while it was there, and I haven't yet noticed any consistency on when it happens (sometimes a cold start is normal, sometimes not; sometimes a warm start is normal, sometimes not; doesn't seem to matter how long it sits while I'm often using my bike for transit in warm weather). Throughout all of this, once I get a normal start the cars runs normally. I'm hoping to have some more ideas on what I can do myself, or what to tell a mechanic.