What Causes Spasms When I Lie Down?

I usually get these light spasms when I lie down on the couch in the evening to watch TV often after doing mild stretching exercises, sometimes jumping on the trampoline); today I experienced a couple while sitting. I am a high school teacher.I take medium dosed of effexor and welbutrin, and low dose of estrgen(natural) and testosterone. What do you think could be the cause? I' (a young) 59.weight about 187, height 5"5"