This may or may not help, but we had a 1976 Chevy blazer that sat for a couple of years. apart from not bothering to change fluids gas etc, we changed the plugs, plug wires and coil, and once fired up, it ran like crap. of course after racing it around the block several times flooring it and expelling lots of smoke, it actually ran decently.
So I guess best thing to do is change fluids and filters, battery, plugs, and start it and drive it a bit to see if it clears up. it probably just needs to burn off some gunk buildup.
P.S. I'm not a tech.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.