I use my car mainly for short trips around town, with an occasional harder run on the freeway. If I drive the car a short distance after a cold start, say a mile or less, then turn the car off for a while, upon restart it runs very poorly for the first 30 seconds or so. Symptoms are as follows; it starts and idles fine, but under acceleration it stumbles, bucks (sometimes fairly violently), and has no power. After a brief while, it feels like it "clears its throat", and then runs fine for the rest of the trip. If the car gets fully warmed up due to a longer initial run, it does not exhibit any poor running symptoms upon a restart. Car is not throwing any codes. Thoughts?