You've just discovered the infamous FSX carb heat bug. :-)
Even though the plane is fuel injected, FSX still makes it susceptible to carburetor icing in the (non-existent) carburetor and, of course, there's no carb heat switch in the A36 because - of course - there's no carb.
Hit the "h" key (default FSX carb heat assignment) and the problem will go away. With the exception of two planes that I know of which have hard-coded fixes for this (the Milviz B55, and the new RealAir B60 Duke V2), I include hitting "h" as part of my pre-takeoff checklist on my fuel injected piston planes. There's no performance penalty as there is in an actual carbureted plane, so I just use it as a magical key to keep the problem from occurring.
Hope that helps,
Scott