Your thoughts begin to gently drift off the plane of reality and you’re about to transition from that dreamy state to complete sleep. Then — suddenly — a part of your body twitches and you’re dramatically jerked awake. Sound familiar?

What you’re most likely experiencing is something called a “hypnic jerk,” according to Ellen Wermter, a family nurse practitioner and Better Sleep Council spokesperson.

A hypnic jerk is a form of myoclonus, which is essentially just “a fancy way of saying ‘muscle twitch,’” Wermter told HuffPost. (Another form of myoclonus is the hiccups.)

“These twitches are not voluntary, and are very short and sudden, often occurring in stage 1 sleep ― a very light transitory stage between wake and deeper sleep,” she added.

During this drowsy phase of sleep, your muscles relax. Your brain sometimes interprets this sensation as “falling,” so it then triggers a muscle contraction. Hypnic jerks, also called “sleep starts,” can happen for no reason and sometimes stem from an underlying issue.

There are certain factors that increase the probability of experiencing a hypnic jerk. These include stress, heavy workouts and certain medications like serotonin reuptake inhibitors (SSRIs).

Sleep starts are common in healthy people, but can be exacerbated by fatigue, sleep deprivation or stimulant use (caffeine and beyond), added Alex Dimitriu, a double board-certified expert in psychiatry and sleep medicine and founder of Menlo Park Psychiatry and Sleep Medicine. 

For the most part, hypnic jerks are benign and nothing to worry about. But if they’re happening regularly and preventing you from falling asleep easily, it’s worth talking to your doctor, Dimitriu told HuffPost.

In rare cases, sleep starts may be a sign of an underlying medical disorder, according to Wermter, which is why it’s always a good idea to check on something that’s abnormal and persistent. For example, sleep apnea ― a disorder where your breathing repeatedly stops during sleep ― can sometimes cause muscle contractions.

“When the airway is blocked and blood oxygen levels dip, the brain sends an arousal signal, sometimes in the form of a muscle twitch,” Wermter said. 

There’s no tried and true way to prevent these nighttime muscle twitches, but you can decrease their likelihood by keeping a regular sleep schedule and keeping yourself in a quiet and comfortable environment, Wermter said.

Controlling your stress levels and being mindful of your caffeine consumption can also be helpful. If you are an afternoon coffee sipper, try to cut back on your midday drink. You might find it helps reduce your hypnic jerks, Dimitriu added.

Try altering your habits or checking in with a professional and see if you sleep tight ― without twitches.