[1999] Lexus ES300 - What is causing a jerk (and engine movement) when shifting gears?

Hello,

Keeping it short, I had a P0300 (multiple misfire) code with P0302 and P0303, meaning cylinders 2 and 3 were identified bad.

I changed out spark plugs 2 and 3 based on the firing order from my car's manual, but now when I shift gears, the car jerks or thrusts forward slightly and the physical engine itself under the hood props up, and goes back down when put on Park. Shifting from Park to Drive to Reverse and so on was smooth before changing the spark plugs.

The RPM stays at about 1100 on Park and 900's when I put it on Reverse or Drive.

What would cause the car to jerk when shifting gears? Would changing the two spark plugs (out of 6 total) cause some sort of imbalance and thus a jerk when shifting gears or is it a separate issue? I only changed the two spark plugs and kept the same wires and ignition coils.

Anything else you need, please let me know.

As always, appreciate the help of the community! Thanks in advance!