Shelley Berman is 80 years old and hot, hot, hot. When he cups his hand over the phone and yells to his wife: "Where am I this week, Sarah?" he's not having a senior moment. Fresh from playing Larry David's father on the HBO series, "Curb Your Enthusiasm," he's got bookings in Las Vegas, feature film shoots and network television tapings on top of his regular slate of teaching classes at USC. Shelley's current schedule would kill a person half his age, which is why, at 44, I'm functioning as his occasional producer, acolyte and coffee bringer ("Last time someone brought me hazelnut -- can't a person get an honest cup of coffee any more?") at 24th Street Theatre, where we're in the middle of a live Shelley Berman minifestival.