Web load testing - what does a wavy response time graph indicate?

I am running a load test on an API using JMeter. When I host the API on the same pc as the test (the database is remote though) I get ok results. However, when I tried running the load test through the same API but hosted on a different pc on the same network, I got this wavy pattern in my test results.

Each of the four grouped lines are response times for a particular API endpoint and the blue line is active thread count. The question is: does this wavy pattern mean anything? This pattern isn't visible when the API is hosted on the same machine as the test. The results are very different and I am thinking this pattern might be correlated to the problem.

I used 200 active threads and no specific configuration which would produce the requests in this pattern.