This study found that powerlifters performing deadlifts produced significantly less force in the starting position compared to other positions. Train exercises like deficit deadlifts and speed deadlifts to improve your strength and power off the floor to overcome this weak position. Mobility work may also be necessary for novice lifters to be able to safely and adequately produce force in this position.
Reference: Beckham, G. K., Lamont, H. S., Sato, K., Ramsey, M. W., & Stone, M. H. (2012). Isometric strength of powerlifters in key positions of the conventional deadlift. Journal of Trainology, 1(2), 32-35.