I'm waking up at night with rapid heartbeat and low oxigen. what could this be?

Need to examine: It is not feasible to provide a meaningful opinion without taking additional history, physical examination and may be some tests. It would be prudent to see your doctor. If you are overweight it may be due to sleep apnea and you should try to lose weight. Wish you good health! - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex, if you have sex.

Low O2: Rapid heart and low oxygen is your body telling you either for circulation, oxygenation or pump problem. That means heart. There may be other reasons as well. You make an appointment to further evaluate