I started my SL65 up this evening after it sat for around two days. The RPMs started jumping around and the car was rocking. It almost felt like it was going to stall.

I allowed the car to continue to idle and see if it would smooth out, but it did not after a few minutes. I shut the car off, restarted, and everything was fine.

No check engine light.

Does that sound like a misfire? Any ideas?

I've had the same issue on my S65. I changed my spark plugs and most of the misfires are gone. I just hope I caught it early enough to prevent damage to the coil packs or voltage transformer. I still have a couple of misfires on the driver's side but minimal. I had never gotten a check engine light either. I'd say start checking the ignition system. Also, it would probably be best for you to have a scanner hooked up to her to see which cylinders are having errors. If it's only one side of the engine, you may have an issue with that coil pack.

Thanks, drove the car today, all was well.

Ill keep an eye on it and will check fault counters is SDS if it happens again.

Also check your battery. I've heard before that on these cars a weak battery can also cause some misfires. You said the car sat for 2 days, maybe your battery isn't holding charge like it should.