Sometimes it can be related to the medication. If you've been on various other ADHD stimulant medications besides the Adderall and had the same results, it's worth talking with your doctor about a non-stimulant. It could also be about when you're taking the dosage. It can sometimes be helpful to set an alarm earlier in the morning than when you actually wake up and then take the dose before going back to bed. Assuming it doesn't work immediately and keep you awake.

A second thing would be to examine your own sleep hygiene. There's lots of good resources online. You may already be doing this, but sometimes there are issues with sleep that may be effected by sleep apnea, exposure to stimuli, caffeine, bedtime routine, etc. Also, are you taking naps during the day? How many hours of sleep do you average? Have you ever used a sleep app on your smartphone or a fitness tracker that records sleep?

When you do experience the insomnia, what is keeping you up? Is it energy? Is it racing or worry thoughts? Is it responding to noises? Is it feeling restless? Certain symptoms of insomnia may be signs of other mental health concerns as well.