When you say that "my heart starts beating really fast" it doesn't tell me how fast it is really going. It might be at a moderate rate and you have become aware of it. So you should time the rate a number of times by counting the beats for one minute. Numbness and tingling in the hands and feet could be due to hyperventilation (over-breathing), which may occur with stress, and would not necessarily relate to your heart rate.
You acknowledge that you are overweight and that your cholesterol is elevated, so you should do something about that. See a physician and get appropriate treatment for your cholesterol with diet and medication as necessary. And while you are at it, tell the doctor what your heart rates are when you lie down at night.
Proper treatment of your cholesterol and weight would significantly reduce your risk of a heart attack, though I should emphasize that there is nothing in your described symptoms that indicate "an upcoming heart attack."