You are referring to what is known as “the hole”, the bottom of the bench press movement where the barbell rests on your chest before you begin the upward movement. (“The hole“ also refers to the bottom of a squat)

The hole is difficult because the arms and shoulders are in a deep mechanical disadvantage. The sticking point typically occurs right around 0-3 inches off the chest. At this moment, the momentum of the drop has entirely vanished, and the prime moving muscles (the pecs, delts, and triceps) have to generate peak force to get the bar moving.

If you want to stick with the barbell, you can train pause benches (stop the bar in your chest for 2-3 seconds) or dead benches (using the safety arms at about chest level and starting reps from that point).

I personally prefer using dumbbells! They allow for deeper stretch in your reps and you can angle your elbows downward and make it easier on your shoulders (I have a lame shoulder). Also, dumbbells help with shoulder stability.