I have a graph which appears to be random but there seems to be a pattern hidden in it. How do I analyze it? The below graph seems to be random but I think the peaks seem to repeat after a certain period. Are there any statistical tools I can use to analyze this?

Edit:
I am adding the plot of its autocorrelation:


If you suspect that there are periodic signals in your data, you can analyse it in the frequency domain.  I would recommend you start by plotting the signal intensity using the intensity function in the ts.extend package in R.  Intensity spikes in the frequency domain indicate periodic signals in the data, and harmonics of these spikes occur when those periodic signals have a shape that is not perfectly sinusoidal.
