MIL/check engine light on for 2 days and now gone. Cause for concern?
 

I have a 2001 Audi TT Quattro 6-speed manual with 50,300 miles on it. The car has been running great...till now. I've just started having battery issues which I believe is linked to the radio which stays on after I turn off the engine, remove the key and open the door. That's an entirely different issue (if you have any suggestions, I'd be grateful!). If I turn off the radio, the battery does not discharge but I found this out only after a few days of the battery dying and jump starting the car. Then one day, at a light, the car shuttered but did not stall and the indicator lights in the car went on and off. Car seemed fine after that. But then driving a long distance, the MIL/engine check light turned on and stayed on for 2 full days but has now gone away. I'm not sure if this is all connected. Should I take it in to get it diagnosed? Is this all connected?