dozing off as a passenger on a motorcycle

I love to ride with my  husband on the back of his Harley, but I tend to become drowsy after 45 minutes and I will nod off for 1 second. I try my hardest to keep my eyes alert but they play tricks on me as though my eyes are awake, but suddently my head would nod off for 1 second before I realize that I've nodded off during the ride.  My husband doesn't want to take me riding anymore because it is so dangerous.   I love to ride with him and I'm so devastated and disapointed in myself that I have to give up this passion of riding with him.  The night before the ride, I tend to have anxiety and wake up a few times during my sleep so I don't have a good night's sleep, but even if I did have a good sleep, I still tend to get drowsy during a 1 hour ride.

Please help! I have never been diagnosed with any sleep disorders.  I want my self to stay awake and alert during the ride!!  On another note, I also doze off with the same feeling during meetings or any classroom training that requires me to sit, focus and listen for 30 mins or more even though I try very hard to keep listening - my eyes just tend to close for a brief moment and I doze again...very frustrating