check engine light-misfire codes

Hey guys I randomly got check engine light codes during my first start up of the day on thursday (on my way to work) and the internal diagnostic system have me p0300-p0306 codes, apparently misfiring from all cylinders. The car starts regularly and stays in idle and I can't really hear anything different but I cleared and it came back on today. Obviously the problem still persists, what do u guys think it may be?

I got gas about a day before the codes came on, plugs were changed at 186k 2yrs ago and I currently have 206k