Is it possible to be on flatline only in the mornings?

So I wake up with no problems in the morning, I eat my breakfast, I'm fresh, then I go to work. As soon as I start I feel like my body looses its powers and energy. I feel drained and lethargic as shit. It doesn't last long. As soon as I have my snack I already feel better. And after lunch I'm ready to go...I usually have no problems for the rest of the day. I feel decent, especially after gym.

Why is this happening? Strangely enough, in the weekends, there's no sign of this feeling. It's saturday and I feel amazing. (I don't work in the weekends) Could it be because I ride the bike 4 kms to work in 10 minutes? I took the bus a few days and it happened then too.

This happened on my previous streak too, at another job also (it was a call-center). This one is in a small warehouse, so it's a way more active job than the other one. But it still doesn't make sense as I wasn't riding the bike there and I would just be sedentary for 8 hours.

Like I said, as soon as I eat something it slowly goes away. I wake up at 6:45 and at 7:30-8:00 in the weekends. I sleep at least 7 hours at night. Is this a flatline or what?