What causes shaking?

[Ailantd]

I think there are 3 main things you have to consider to avoid that: mixture setting, water radiator and oil radiator. In 109 E4, for example, ( automatic prop pitch ) with both radiators open is enough to avoid shaken.
Check also your prop pitch if manual. It can cause you to over rpm the engine when diving at high speed.

[drewpee]

If your engine shakes it some thing you've done or not. High revs and/or temp. Try getting used to lower your revs when cruising and always keep a close eye on temps. Cut the throttle befor diving if you don't have time to set the prop, it only takes seconds to blow the engine in a dive.