[ACRobb]

Hello, I could use some ideas on how to troubleshoot my car. It has a solid check engine light with codes:
1. P0300 “Random / Multiple Cylinder Misfire Detected”
2. P050D “Cold Start Rough Idle”

Here’s a description:
-Initial crank starts around 1.2k RPM then after ~30 seconds it drops to normal around 600 RPMs. Shows solid check engine light but acceleration feels normal.
-This happened before but had a flashing check engine light with a stabilitrack light coming on as well. I heard an unusual noise (sorta like whining) from the engine and it felt sluggish when accelerating. I cleared the code and the issue went away for a day or two (except for the high initial idle with cold starts).
-I have replaced the spark plugs, coils, and wires. Before I did this it gave off codes P0308 (cylinder 8 misfire), P050D, and P0128 (coolant thermostat).

The next step is a compression test. I’m open to other suggestions.
2016 Camaro 2SS, automatic, 68k miles, and is stock.