The reason why you tend to fall asleep near noon is your sedentary work (like me).
Whenever I'm in front of the computer feeling like I want to fall asleep too early, what I do is go here: Digitally Imported Internet Radio
choose the hardcore music channel (the really pump-you-up dance music, it's almost always never obscene, have drug references or anything really offensive, it's just really hyper.)
And just dance around however I feel like it. I don't dance around like I'm exercising, trying to push myself to exhaustion. I just do it to pump up the blood and have some fun. A few minutes of that and all of a sudden I'm alert and ready to go.
Get some exercise! Use something like crossfit (google it)