When i am asleep, i am suddenly jolted awake with what seems like an extremely strong single heart beat. extreme chest jolt. what could this mean?

PVC possibly: Several things come to mind, but you almost exactly describe the feeling some patients get when they have a premature beat (these are typically benign), the beat after a premature beat typically feels like a jolt. Other reasons for this type of a feeling could be OSA and related sleep disordered breathing maladies.

Not a heartbeat: This most Likely is not a single heart beat but may be a myoclonic jerk which may occur when one is somewhat between a sleeping and an early awakening state. These are not considered to be serious. Consult a neurologist if you have any further concerns about these episodes.

Hypnic jerk: you may be experiencing what is called a hypnic jerk when one suddenly wakes up suddenly from sleep. It usually occurs when just falling asleep. It is normal. It is often caused by being overly tired, stress, irregular schedules. Despite this being the most common cause other causes can be sleep apnea, periodic limb movements, arrhythmias to name a few.