When i just fall asleep my heart starts to pound and i feel a sense of panic and can't fall asleep. what could be causing this? what can i do 4 it?

Sleep onset panic: Keep your thyroid under control and get a physical, ekg and labs. Unlikely sleep apnea because you state it happens just as you are falling asleep. One theory is that there is a build up of carbon dioxide in the body, a condition that is known as "false suffocation alarm" that causes the body to react with strenuous breathing and rapid heart rate . A risk is that you could develop fear of sleep. Please see a psychiatrist or a cognitive behaviorally trained psychologist. This is not due to fear of dreaming because this does not occur as a result of bad dreams. It is too early in the night and has nothing to do with rem sleep.

Sleep issue: Even though i agree with dr. Jacobson but if you have tossing and turning all night, if there is snort arousals and if you are worse on back , if you are obese all these are signs that you may need sleep study still.