Engine shake after long drive

This happened just today. I drove from Los Angeles to San Diego, about 120 miles. Everything went well. After stopping to sign a contract with a client (which took about 30 minutes) I started the car up and got ready to drive back to Los Angeles. The ICE kicked in, and then started to shake very violently. I turned the car off and restarted again. The ICE kicked in again and started to shake very violently. I floored the gas pedal and then it stopped.

After driving 120 miles back, I stopped the car and went to second client to sign another contract. This time the car was stopped for 45 minutes. The ICE didn't start til after I backed up and pulled forward. It shook very hard again. I floored the car and everything went back to normal. Drove another 90 miles and everything went fine. Stopped by my office and the car rested for 4 hours.

After 4 hours, as I braced for the worst, the car started just fine with no shakes whatsoever. Stopped by the market on the way home, about 10 miles later, for about 15 minutes, and the car started to go just fine as well. After pulling out the parking lot, the engine stumbled just a little, perhaps 2 seconds, as the ICE kicked in.

MPG and power all feels the same. Spark plugs were changed 1000 miles ago.

From my searches on the forum, I gather that it may be one of the coils? or EGR needs cleaning? I under the coil issue, but EGR? Does clogged up EGR effect the engine right as it starts? I've been wanting to take the EGR apart to do a total cleaning, but with COVID, my businesses closed down so I have to get 3 different part time jobs to get by, haven't got a chance to do so.

Thank you in advance for any advise.

 

Purchased the car at 160k miles. Had an indy checked it out, everything seems fine. It's currently at 175k miles. Oil is clear, not milky, it's not gaining or losing oil.

Do you mind me asking why would you come to the conclusion of blown head gasket?

 

Thank you for the reply. Just went outside and checked again. Oil on dipstick clear and at full mark. Coolant at full mark as well, as the engine is still warm. I understand that if it's the dreaded head gasket, it's cheaper to find another car, or hunt down a used engine and have an indy install it. If.... IF... IIIIFFFFFFF.... it's the head gasket. Is there any difference in going to the dealer to have it diagnosed now? or drive it til the engine tears itself apart? Other than getting stranded on the side of the road? I've sent gasketmaster a message to see if it's feasible to have time come down to do the change even just as a preventative measure.

 

Started the car and stood behind it for a few minutes. Smelled the familiar sweet smell of burned coolant, so I contacted gasketmasters and was told not to run the car since it's very likely it's a headg asket issue. Quoted $1550 to come to Socal to fix. But when I asked him when he could come, didn't get a reply.

Stopped by the local prius shop that took care of my batteries previously. He confirmed head gasket by opening the coolant reservoir while it was hot. Mentioned that if there's an issue with the head gasket, the pressure will be higher and the hissing would last much longer than a healthy engine. Coolant level has dropped almost an inch since last night. Was quoted $1200 for a head gasket job. He mentioned that since the cylinder had water in it and couldn't compress, there's a good chance that the piston rod could be bent. Pulled one of the rods from a car in the shop and showed me. Quoted me $1800 for a rebuilt engine installed. Which he just happens to have one sitting on a crane about to be installed on the prius with the bent rod. Since I need a car to drive around, asked him to give me that motor and was told that my car would be done by tomorrow 12pm (it was around 11am when I went there). Also asked him to make sure that the EGR system is cleaned out as well.

Fingers crossed that everything will go well. Anything I should ask or examine when I pick up tomorrow?

Thanks for the input and the gasketmaster referral. If i have a second car sitting around, I would've waited for their response.