The warm up is very important - that's pretty much common knowledge with everyone that trains regularly. But how you warm up certainly plays a part.
Typically, most people choose either a treadmill or a bike. The problem with both of these is the fact that it neglects your top half.
Prepare your upper body better for lifting big by first lifting light. For example, choose w bench-press weight which sees you able to do 15 or 20 reps with moderate ease. Count to 30 and bump it up, doing only 10 to 15 reps. Then once more with 5 to 10 reps.
That'll just about do it...