Hello,
not sure there is anything useful to say after Tom has spoken, but just on the offchance I would like to offer my 2p.
I have been looking for an answer to your identical question for a while. Recently, I seem to have finally sussed it, and managed to find a cue that appears to work (to be confirmed with heavier weights).
What I do, is to think about starting the pull with the hips. I think of my hips as the first thing that moves upwards. The mental model that seems to work best is 'just raise your hips'.
With any other cue, I was starting the pull 'with the shoulders'; with this, I can see the whole pull works better, the back keeps the angle relative to the floor for much longer.
Hope this helps, although clearly YMMV.
IPB