2002 Grand Cherokee issue, need help please

[kieranone]

Hey Guys
so i sold my 1998 sport and got into a 2002 grand Cherokee v8 4.7l
Truck is in great shape but i have a problem .
1) had it scanned with an odbII nothing came up while running
2)same results with key in the ignition.
No eng light on at all.

It was somewhat cold this morning and when I started it (didnt take any longer than usual it sounded like it was grinding as it started)fairy loud. I got my girl to start it as I was under the truck and sounds like either the starter or the cat?

It wasnt doing this as it was warm but noticed today when it was parked under ground that i could still hear the noise just not as bad. Out of the 5 times I started it today it did that twice just not as loud as it was this morning .

I know I can buy a new starter but wanted to see what you guys had to say before I do that.Any ideas of what else it could be?
My thoughts were if it was the cat it would do it evertime I start it?
please help.
none of the dealers I talk to say they recognize the prob so I figured someone here would.

thanks