Another factor may be lifestyle choices. Not saying you are affected by these, but being older, drinking alcohol at night, or ingesting caffeine(even tea) past,

Another factor may be lifestyle choices. Not saying you are affected by these, but being older, drinking alcohol at night, or ingesting caffeine(even tea) past, say, 2 PM, certain medications, not following a set time to sleep, or getting woken by the sun are all potential factors, so you should continue to consult with your health care professionals.