Any time you experience a Limp Home Mode - you need to take it to the dealer so they can pull stored ECU fault codes and address those problem.
It happened to me last year. The dreaded service engine soon light, reduced power, wont go above 5 miles an hour.
The only remedy: Parked the car, let the engine cool down to reset everything, engine restarted fine.
I took my beast to the dealership. They pulled codes and let me know that what I experienced is a know issue and it requires update of software to the latest and greatest revision.
Took them over 8 hours to update software. Got my car back the next day.
Zero issue since then. Beast has been running trouble free for over a year now.