What causes pausing of the breathing during sleep at 25 years old?

Sleep apnea. This could be related to sleep apnea, meet with a sleep specialist or your pcp so that they can examine you and possibly even get a sleep study.
Sleep Apnea. Sleep apnea is a condition caused mostly due to obesity and makes person's tongue fall back during sleep and cause a pause of breathing called apnea. These people snore during their sleep.
Get sleep study. Stopping of breathing is not normal. You may be describing "sleep apnea". Most common type of sleep apnea is when your airway gets blocked during sleep. Sleep apnea may also caused by the nervous system failure in signaling the muscles responsible for breathing functions. Whichever the type, it is obvious that this can be life-threatening. Please consult a doctor before sa kills you in sleep.