Here are a couple of stretches for the Triceps!
The first stretch is a simple across the chest stretch. Place one are across your chest and gently pull on the elbow using the opposite hand. Hold for 10-15 seconds then repeat on the other side.
The next stretch is the over-and-behind stretch. You may be seated or standing for this stretch, as long as you keep your back straight and tall. Put one hand over and behind your head. Using the other hand, gently pull your elbow closer to your head. Hold for 10-15 seconds then repeat on the other side.
If this is too hard on your shoulders, you can use a towel to get the same stretch, see the clip below. Still bring one hand over and behind your head, while holding one end of a towel. Then put the opposite hand behind your lower back to grab the towel. Gently pull down on the towel to feel the stretch. Hold for 10-15 seconds, then switch sides.