aqfrenzy

hi all, i have a w208 230k under 58k miles, around 8000 miles until next service (last full service was done in sept). recently i have noticed the car is feeling underpowered, it feels like the kompressor part of the engine has just disappeared... the car is no longer punchy with acceleration. wondering if anyone knows what the possible problems could be before im forced to take it for a health check?
also seems to be the case that this problem started pretty soon (or immediately) after a flat battery so im wondering if this could have anything to do with it, perhaps ecu?