Hey, I have a very similar issue with mine too ..... when I'm motoring and the fault happens, I just zap it into neutral and then re-start the ignition ..... at whatever speed, it seems to work ok then .......... until the next time.
No rhyme nor reason to it and sometimes it is just absolutely fine....... with no issue for weeks/months on end
I have, just yesterday emailed my indie mechanic chap for an explanation and for him to ponder the big Q.
When I get a response I will let you know.
He has been aware of this issue for ages but didn't have a clue !!! He initially cleaned out the throttle body but that hasn't seemed to resolve
I have thought maybe it's an Oxygen sensor.
Malc