my Toyota mr2 won't start. I was driving down the freeway and I heard little rattle so I put it in neutral and pulled over the car turned off as I was in neutral and wouldn't start again.

Timing issue,the sound you heard was more than likely a timing idler came loose,dropped the belt and jumped timing,if it only clicks,means you may have damaged your heads.

where is the timing idler

Inside the timing cover belt side of motor.You will have to remove belt,s and some pulley,s to remove cover.

Check for lose belt and or chain that will be your sign.