1st I strongly recomend Cinemachine
https://unity.com/unity/features/editor/art-and-design/cinemachine
This makes doing things like this with cameras a lot easier. If you have this then what you could do is set up 2 vCams
1 that is your stable cam 1 that has camera wobble on it (feature of Cinemachine) set to a high frequency so its jaring
Then to start the shake you simply turn on the wobble camera ... to stop it turn it off.
this will work if your stable cam has a lower priority than your wobble cam ... so no need to turn stable cam off ... wobble cam will override it and the system will blend between them so no jerking at all.
Finally put both of these in a GameObject to act as a common root or have both of them track on the same target ... for info on that and what I mean their please study up on Cinemachine.
This tool will let you do most things with zero code, the rest you can do with very little code ... highly recomend it.
This makes doing things like this with cameras a lot easier. If you have this then what you could do is set up 2 vCams
1 that is your stable cam 1 that has camera wobble on it (feature of Cinemachine) set to a high frequency so its jaring
Then to start the shake you simply turn on the wobble camera ... to stop it turn it off.
this will work if your stable cam has a lower priority than your wobble cam ... so no need to turn stable cam off ... wobble cam will override it and the system will blend between them so no jerking at all.
Finally put both of these in a GameObject to act as a common root or have both of them track on the same target ... for info on that and what I mean their please study up on Cinemachine.
This tool will let you do most things with zero code, the rest you can do with very little code ... highly recomend it.