It's not the Trimix. It's Nitrogen and Depth.
Switch to Heliox and see how you feel.
After deep trimix dives, John and Rod would take naps, while I would run around the boat chattering like a monkey for an hour. (I was on 14/86 Heliox).
'Course, I used to smoke 2 packs a day too, so running around was nothing unusual...
Kevin.