My car wont start or sometimes starts and shuts off?

[Pernell]

I recently got into a car accident december 7th. The other drivers insurance sent in the check to buy a new car and in a rush we went out and bought a 2004 saturn ion. After the pre-purchase inspection they said we got a really good deal but we later realized that my car sometimes tries to turn over n doesn't. it cranks but doesn't turn on. sometimes its only a click when u turn the key to start. at times when it does start it shuts right back off. any help would b appreciated