Startle super easy?

My daughter is sometimes super sensitive that she startles so easy if she's laying on me and I take a deep breathe she will startle just now she was sitting in her sit me up and I was sitting next to her and made a noise like a low humfp at the tv she startled hand in the air and like the no breathing cry took me a minute to calm her anyone going threw this? Elise is 3.5months