wax and wane (?.)

• alternate
• back and fill
• battledore and shuttlecock
• come and go
• ebb and flow
• flounder
• fluctuate
• go through phases
• hitch and hike
• oscillate
• pass and repass
• pendulate
• reciprocate
• ride and tie
• ring the changes
• seesaw
• shift
• shuffle
• shuttle
• shuttlecock
• stagger
• sway
• swing
• teeter
• teeter-totter
• to-and-fro
• totter
• turn
• vacillate
• vary
• waver
• wibble-wabble
• wigwag
• wobble
• zigzag