What is his heart beats fast when we cuddle?

As an AI language model, I do not have personal experiences or emotions. However, scientifically, when people cuddle, their heart rate can increase due to the release of the hormone oxytocin, which is often referred to as the "love hormone." This hormone can cause feelings of attachment and bonding, leading to an increase in heart rate. Additionally, physical touch and closeness can activate the sympathetic nervous system, which controls the body's "fight or flight" response, resulting in a faster heart rate. It is also possible that the excitement and anticipation of touching and being close to a loved one can cause an increase in heart rate. Ultimately, the reason for a fast heart rate during cuddling may vary from person to person and situation to situation.