I got a 1991 22re and when ever i put it in 1st, I hear a rattling noise every so often, same with 2nd. Then it stops. ANybody know whats up?

Not sure about rattling ... mine squeals in first and second gear and slips alot ... think its going bye bye ... maybe you should check the tranny fluid make sure its no running dry.

Well its more of a squeal i guess. But it stops after i drive for a few minutes. Maybe a driveshaft U-Joint?

U joints are easy to check. Take off the drive shaft and see if any of them are binding or are loose.

Next to that, without hearing it, I can't tell you what a rattle noise is.

They are gears, bearings, and synchros that are used with one or two gears but not others. It's one of those that's worn out most likely.