You have my sympathy....
I have the same startle response and have had it for decades. Mine came from Lyme Disease...never had it before that. It is not only noises, it is sudden movements like my cats silently jumping up on the bed when I don't see them coming.

I have found MS and Lyme Disease have many overlapping symptoms.
Many times folks with LD are incorrectly dx'ed with MS and vice versa. Me included.

On my first brain scan had a lot of what they called back then, UBO's that apparently looked like the same brain lesions caused by MS.

I make my family and friends nuts with my oversized startle response because I sometimes shriek or drop things. It is SO out of proportion to the stimuli. I have a friend who has had several concussions and he said he has the same startle response.

Just another symptom to try and grin and bear.
My best, D.