Weird, spontaneous, strong vibration at idle

[O2ShootTheJ]

Hey guys, so a little background. 2008 e92 M3 84k miles, VF650 kit, just had rod bearings replaced with BE bearings 300 miles ago. Car is my weekend driver and gets driven about once a week on average.

I noticed 2 weekends ago when I had the M3 idling it seemed like something turned on and started vibrating and vibrated the whole car for a 5-10 seconds and then went away. I was unloading groceries into my house and honestly thought the engine was about to go. But it subsided and the car seemed to be running normal.

Then I had the same exact thing happen 3-4 times this past weekend. I've only noticed it at idle and the car seems to be running fine otherwise. The car also started really rough and threw a code for an O2 sensor after it sat for 2 weeks while I was out of town, but i cleared the code and its never come back and started fine since. Not sure if any of that is related.

Does anyone have any idea what it could be? Wasn't sure if it's because the car needs a better tune (it does) or maybe an injector is going bad or something like coils/spark plugs?