My fave is those who try and zoom climb...
Higher alt set in mcp, open climb selected and speed wound back. Auto thrust FMA announces THR CLB, engines roll back to idle thrust
(just have to wait until climb thrust achieved before waiting to wind speed back)
This doesn't happen every time, just when it's the most awkward moment for ut to happen!
This happens every time you have a significant positive speed trend and the autothrust tries to avoid Speed excursions.
1st Option initially engage expedite climb... Your engines will spool up almost immediately and once you are established in a climb with your thrust set in climb select or manage your speed
2nd option ... While in level flight select a speed at least 5 knots below your desired climb speed ... Once cleared to a higher level : set cleared alt on your FCu - select op climb or climb ... And then increase your selected speed by 5-7knots ! Your autothrust will set your engines immediately to meet the selected speed
then you may adjust your selected speed to increase your rate of climb !