The other day while I was driving home, my car(2004 350z) dramatically lost power, acceleration, and was shaking rough, sounded like a tractor. The check engine light came on flashing. I got home pulled the code, and it said P0300 misfire but didn't tell me what cylinder. What could it be? Thank you in advance.

 

Look here for possible causes of the problem you describe:

https://www.autocodes.com/p0300_nissan.html

 

Code P0300 occurs when the ECU can't determine which cylinder is misfiring. This can occur when multiple cylinders are misfiring at erratic intervals. You should look for a cause that affects the entire engine (bad gas, for example) and not just one cylinder.