Weird idle

[E30rid]

I have a 89 325is that I bought about a month ago and when I start it up the revs go up to about 2k. After it comes back down it randomly goes up and down every once in a while.
Is this something to be worried about?
Thanks

[diggity_1031]

I had the same problem and chased after a small air leak around the maf. Turned out to be a loose plug on the maf with the clip missing. Try checking for unmetered air leaks.