Loud knocking from engine once at startup

Hey everyone.

So I have seen other people have similar issues that they heard knocking when they start it up cold and etc. So my issue is i have started my car one morning (after sitting all night from 8pm), and it started perfectly fine and engine kicked in like normal. Then I moved it into the driveway from the side of the street, maybe like 20 feet.

So after having the prius sit for roughly a few hours, i start up the car and i heard really loud knocking noise and the engine shaking violently and I felt the car also shaking a bit too as a result of this i immediately turned off the car. Afterwards i turned on the car and the engine turned perfectly fine without the loud knocking.

I drove home perfectly fine (roughly 30 miles) it did not give any problems at all. It's been a few days after this incident and nothing has happened since. My worry is with the little research I've done. I need to change the head gasket. Is this something i need to get done? I would like to see what I need to get done so I can fix it up and not have this for another million miles (figuratively) to make my car last a while longer.

It's a 2014 prius two. Currently has 136k miles i had never had any problems until now. I haven't even changed the spark plugs...

 

Holy smokes, that's just crazy. My timing chain hasn't given me issues at all. I know that for sure. It's very quiet from what I can tell. I am trying to see what I can do before i actually take it to the dealer for diagnostics. But the gasket i can fix myself for sure. Just trying to do preventative maintenance just in case of anything.

 

I'll take a look to cleaning it up this weekend. What would i use to clean the egr and intake manifold? Not sure how it clean the oil catch can either.