Whenever I turn my car on or off, the first few or last seconds it hisses. I don't know if it's a leak because there are no leaks in my engine bay and it stays cool in the car, it's been doing this for a few months with no major issues...has anyone else experienced this issue and how did you fix it?

 

a vacuum leak will hiss.

pop the hood with the engine running and follow the sound.

 

depress and hold the brake pedal ...shut the car off...if the pedal pushes back...the vacuum booster is leaking

 

Turn off the a/c before you turn off the engine and see if the hissing goes away.

 

..a/c yes, but would not explain hiss at start up