My Jetta vibrates when driving and check engine light flashes.

So, I bought this Jetta off Facebook for cheap
a couple months ago. It’s a 2004 1.8T. It
seems like one thing after another keeps
happening. First, I replaced the water pump,
hoses, and a few other things that go along
with the coolant system because my car kept
overheating. I had my car out of the shop for a
week or so and then I had to replace all of the
spark plugs, wiring, and ignition coils. I also
had my mass airflow sensor replaced. It has
been about another week and now my Jetta
just started vibrating along with the engine
light blinking again. The mechanic I took it to
said it was because of the spark plugs, coils,
and wiring, but I guess not. Car runs and
drives fine other than that. If it’s vibrating or
shaking when I’m in park, the car idles
differently.