How to choose oscillating intervals

I have a signal from a sensor and need to isolate the intervals in which the pressure was unstable (oscillating), I have tried filtering the signal using the filter designer, but in different intervals the oscillations have different frequencies so it has not work. Has someone solve something similar and can give me an idea of how to do it?

[Akira Agata]

Seems that envelope and/or spectrogram functions would be help somehow.

If possible, could you upload your signal data to allow people here try their solutions?