Since I have seen every episode an average of 40 times, I try to pick the ones on the low side of average.
This means, of course, I find myself often in the 3rd Season of late.
So, if you are in need of sleep, give my plan a try. Nothing like "The Empath" to induce rest. Still awake? Try "Mark of Gideon" or "The Cloud Minders". "Lights of Zetar" would otherwise work, but I'm such a huge Jimmy Doohan fan.