Dick Jitters
When one has consumed too much Viagra (or any e.d. drug) and is having problems. Since the chemical involved in stimulating the penis is similar to caffeine, and since one can get the "jitters" from drinking too much coffee... hence the "dick jitters."
I wanted to make sure I really knocked the socks off that blonde the other night, so I took two Viagra... but I ruined everything when I got the dick jitters!