Violent shake when starting car? Immediately goes away after startup.?

When I start my car, it will jolt violently until it has started. Startup doesnt take any longer than normal, its just when it turns over it shakes pretty hard for a split second. It doesnt happen every time, maybe half the time I start it. Once it is running, nothing is out of the norm. It runs and shifts... show more When I start my car, it will jolt violently until it has started. Startup doesnt take any longer than normal, its just when it turns over it shakes pretty hard for a split second. It doesnt happen every time, maybe half the time I start it.

Once it is running, nothing is out of the norm. It runs and shifts smoothly. Any idea what this could be?

2015 fiesta SFE (3cyl 1.0 5 speed manual) 55k miles.

I know that these 3 cyl engines are shaky by nature, but it hasn't done this in the past. At first I thought engine mounts, but it seems like if it were the mounts, it would do it every single time I started it and that's not the case.

Also, it doesnt matter how long it's been sitting. It has done it when it has been sitting for 3 days and it has done it after its only been sitting for 15 mins.
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