After the Phantom 4 the Spark is my first quadcopter with foldable rotors.
I have been starting and taking off with the rotors folded which works well but has the Spark shuddering while the props unfold.
Do you recommend manually unfolding them before flying? Could there be damage if this isn't done?
THANKS!

Yes unfold them, if one gets a little stuck it will throw balance of and it might cause spark to turn over, same is recommended for Mavic.

Entirely up to you...I've NEVER unfolded the props on my Mavic and owned it since October 2016 with no issues

I don't unfold them.  I have both a Mavic and a Spark.  

Thanks for sharing!

Unfold them manually so you could pre-check before flight. Mainly for safety!! : )