I get it too
I used to workout 5-6 days a week, pretty high intensity. Now, I try to alternate the more intense with the less intense. The only thing with us Catheletes is we tend to think that the only benefit is when we are just working at 85% to 100% of max, and it turns out that the benefit from the workout comes in the recovery. So what I'm trying to say is when you want that rest, take it. Thats your bodies time to build muscle and bone. You can't actually build bone when you are awake. Thats one of the reasons babies sleep so much. I learned this when I had to re-grow much of my toes (they had turned to powder when I broke them running one time.) I was so sleepy.
So, in answer to your question- yes I can feel super sleepy. I need to be restful and quiet for at least a couple of hours after. I liked one of the ladies ideas to do it in the evening, but I find I don't have enough energy to really fly over the step unless I'm fresh in the AM. Thats just me though, and it may not apply to you.
Are you getting enough post workout nutrition? The only other thing might be not enough potassium, we sweat it out when we do Cathes.
(yes I tend to refer to my entire workout collection as 'my cathes'.)