Guaranteed method [fine print:this is not a guarantee]
I've had it for years. I can trace it to a gymnastics injury from when I was 21 (20 yrs ago) The cause is different for different people. For me, it's not a herniated disc; rather the sciatic nerve seems to be pinched where it comes out of the that hole in your hip (called the sciatic notch!). The nerve is sandwitched between two muscles that also come out of that notch. I'll bet this is pretty common, and that's why stretching really helps. I used to get so bad, at least once a year, that I couldn't even stand up straight for a week. I went to a chiropractor and a medical massage therapist and, after learning the right way to stretch, am rarely plagued by pain or problems any more.
I basically massage the muscles where the sciatic nerves leaves the hip. I lie on the floor and cross the foot from the troubled side of the leg onto my other thigh (sort of like you do when you cross your leg while seated - the "manly" way). Then I place a baseball, one of the softer kind, on the troubled area of the hip and roll around on it for about five minutes. It hurts like hell, but the pressure somehow relaxes the muscles. Between that and stretching the hamstrings EVERY DAY (you know: sitting, legs stretched out in front, keep back straight, lean forward, don't bounce, just keep leaning, eventually so that you're pulling on your feet). Eventually you'll get so limber that your chest can touch your thighs.
Guraranteed to improve the pleasure of riding your ducati.