Start car using arduino

I want to make a project that will allow me to start the car by remote do i need to use relays ? i am really n00b at electronics please enlighten me!

do i need to use relays

Yes or a large SSR (solid state relay) of the type that will handle DC (most are AC only)
You can also use large logic level FETs to switch the current required to turn on your starter motor relay.

sub’ing to thread. (sounds like a fun project)

Using a relay or mosfet to turn on current to the starter relay would be quite straightforward. However, for most cars I have driven, you also need to turn off the current once the engine starts. So you'll need some sort of rpm monitor to know when to turn it off. If it is a petrol/gasoline car then you can probably pick up the rpm from a wire close to one of the spark plug leads. For a diesel, you'll need to think of something else.

The other issue you may face is that most cars (at least here in the UK) are manufactured with engine immobilisers as a security measure.