Intermittent engine light flashing

[Liam5469]

Hi , first time posting on here, 

I bought an a3 1.4 Tfsi 2016 with 64,000 miles on the clock , it had a misfire so spark plugs and coil packs were changed . Had car back and was rough idling and had an intermittent flashing engine light would come on for around 10 seconds and then go off. Took it back and was told it was a carbon build up , they’ve cleaned the carbon build up and now it’s a lot smoother on idle and the car drives perfect without any misfires to my knowledge however my engine light just came back on and flashing for around 10 seconds again and went off. 
This has been a problem since getting the car however it only comes on every few days or couple of hours of driving time, can anyone help me out please as to why this is happening as it’s driving me mental .

[Steve Q]

How long have you had it and did you buy it from a dealer? If bought from a dealer in the last 30 days it's their responsibility to repair it free of charge as you can return the car for a full refund In that time.