Appears to be GPU downclocks at regular intervals. Could be bottlenecked by the CPU or it could be hitting thermal limits. Does this behavior only happen in Warzone?
Post your system specs.
Run a benchmark (3DMark, Furmark, etc.) and check for similar behavior.
Ryzen R7 5700X | B550 Gaming X | 2x16GB G.Skill 3600 | Radeon RX 7900XT
Ryzen R7 5700G | B550 Gaming X | 2x8GB G.Skill 4000 | Radeon Vega 8 IGP
Ryzen R5 5600 | B550 Gaming Edge | 4x8GB G.Skill 3600 | Radeon RX 6800XT