What should be my spark-submit options for better performance and now Heap memory issue

Question

I have 1 driver and 6 core instances with 16GB ram and 8 cores each. I am running spark-submit with below options:

spark-submit --driver-memory 4g \
    --executor-memory 6g \
    --num-executors 12 \
    --executor-cores 2 \
    --conf spark.driver.maxResultSize=0 \
    --conf spark.network.timeout=800 job.py

I am getting Java heap memory error multiple times, I think there is something wrong with the options can someone help me out with this.

Thanks