Cut a periodic signal

Hello,

I need to cut a periodic signal collected by an accelerometer. As you can see here, the signal is approximatively periodic (the period is not perfectly constant), how can I find all time index wich separete the signal ? I have smooth the signal but now don't know what to do.

See my screenshot attached.

Thanks you a lot in advance

[Adam Danz]

For starters, I'd smooth it and then use findpeaks to get the indices of each peak.

[Adam Danz]

You could also try autocorrelation.

[Eglantine Collet Manent]

Thanks, findpeaks works perfeclty !