No, it is not bugged, me thinks. I occasionally have this when something is not working well with my plane. Either damage or badly set up. Perhaps you experience turbulences. Usually it is quite smooth. So dear dev team, don't turn it down.

Another thing that could cause this big shaking in the RAF planes is when you get very high. Then the Merlin constantly missfires. This is though not a problem of the head shake but a problem that makes ALL planes not go to their ceiling altitude currently. This issue has already been addressed though and I am sure the dev team is working on it.

I think the planes should shake to a certain extent naturally but that is just a guess. Would like to know the opinion of a real vintage ww2 ac pilot.