Like his friend Waylon Jennings, Johnny Cash is going to undergo heart surgery. Cash, who recently lost another friend, Roy Orbison, to a heart attack, will have the operation Monday at Baptist Hospital in Nashville, where Jennings is recovering from a triple bypass he had earlier this week. Cash, 56, went to the hospital Tuesday for a checkup and the decision to operate came soon after. "John had no chest pains," said Reba Hancock, who is Cash's sister and manager. "He was just experiencing a few problems and went in for some tests. What they found was they think might be some blockage." Cash was hospitalized earlier this year for laryngitis and bronchitis.