No acceleration

Hi everyone!! I am a new member and am hoping you all can help me out.

Here's a run down of my car issue:

I have a 2002 Hyundai Elantra with about 106k miles. I got the car from a family member about 4 years ago so I don't know too much about maintenance prior to my ownership except that the wrong power steering fluid was put into the vehicle at one point which has led to a minor squealing when the wheel is turned after sitting (proper fluid has been in since my ownership).

Here is my MAIN concern which happens on occasion and isn't consistent. When I turn the car on, it is an automatic transmission, the car does not initially accelerate when I step on the gas. The car will slightly jerk forward a little bit with no juice for a few seconds and then accelerate as normal. The problem then stops. It will NOT occur at stop signs or red lights, only after the car has sat for a little while and is then started.

I am not sure if it is related, but my father-in-law recently replaced the air filter and spark plugs. Also, my airbag light has been coming on quite frequently as of recent.

ANY advice/insight?!?!