This may have nothing at all to do with your problem, but I have the exact same car, and a few months ago I misadjusted the Bowden cable trying to eliminate a flaring shift and it exhibited the same symptoms until I reset the adjustment.

Probably wouldn't set a Code 10 though (could that have been set by another unrelated problem?)

And, if it does have to do with the throttle linkage, only reason why it does it sometimes and not others is that something is broken in the linkage and catches occasionally.