The simplest way to cycle animation is to set the Before and After Extrapolation to Cycle or CycleOffset.

1. Add the channels that you want to cycle to the Channel List.

2. Click RMB on the left column showing the selected parameter labels in the Channel List.

3. Select Channels > Extrapolation and change the extrapolation mode to Cycle or Cycle Offset.

One way to do this is by using the cycle() or cycleoffset() expression in the Animation Editor.

1. Add the parameters that you want to cycle to the Channel List.

2. Set a keyframe at frame 125 in the Graph view of the Animation Editor.

3. Select the channel segments from frame 25 to 125.

4. In the Function menu, choose cycle() or cycleoffset().

If you want to create actual keyframes for the cycle, use the Dopesheet in the Animation Editor.

1. Add the parameters that you want to cycle to the Animation Editor.

2. Switch to the Dopesheet view.

3. Select frames 1 to 25 (inclusive) in the All Displayed Channels row.

4. In the Edit menu, choose Copy.

5. Select frames 26 to 125 (inclusive) in the All Displayed Channels row.

6. In the Edit menu, choose Paste Special ▸ Cycle (or Repeat).

For more procedural cycling of animation than the cycle() or cycleoffset() expressions, you can use Motion Effects.

1. Add the channels that you want to cycle to the Channel List.

2. Click RMB the playbar and choose Motion Effects ▸ Cycle.