SLow down or shift up! Inn the message center. What does this mean?

What is your question?

Check engine light flashes with the message slow down or shift up. Red triangle with exclamation point! It does it in auto trans mode or M mode. Then cat starts vibrating

What makes this problem better or worse?

Just putting it in drive. Dosnt stop till i park and put the shifter in park

How long has your 2005 Volvo V50 had this problem?

2 weeks but I'm afraid to drive the car.