On initial start up, the 'knocking/rattling' sound will occur for about 1-2 seconds but doesn't happen every single time I start the car.
On harsh acceleration (off standstill only), the 'knocking/rattling' sound will occur for about 2-4 seconds - also doesn't happen every single time but majority.
Can it be a spark plug by any chance? I've changed 3 of the spark plugs about 12 months ago but the 4th spark plug (drivers side near firewall) I could not get out as the coil sleeve/bolt keeps spinning (btw any trick to getting it out considering it's so tight next to the chassis rail?)
Here is a video of the startup knocking which you can hear (from 2-4 seconds):
https://www.youtube.com/watch?v=_7N22yg ... e=youtu.be