During your training, you have tired out your muscle fibers and they cause the muscle to twitch or shake as the body tries to control them. You have also depleted some of your potassium and calcium resources for a short time. I think you will be just fine. Very high weight and/or high pace of training causes this at a high rate... GOOD JOB!!!
I happens with high weight low reps too when you're close to failure. It means you're working your muslces hard, which of course means you're doing it right.
Yes in short that means your pushing yourslef. Keep going