Falling asleep on the sofa…

[MonkeyTennis34]

This obviously isn’t a huge health issue but it’s bothering me.
We usually settle down to watch something on TV about 8pm and within an hour, sometimes less, I’m fast asleep.
I’m 55, active…I don’t feel this should be happening at this stage in my life.
Any ideas why it’s happening or is there anything I could take to help?
tia

Thyroid or a vitamin deficiency?

I've been doing that since my my early 30s. I think it's perfectly normal.

I've also always needed a lunchtime sleep wherever possible. And I still sleep for 7 solid hours a night.