If the rattle is accompanied by your oil light staying on, then you definately have a problem with not enough oil pressure at start up. I doubt it's a worn timing chain. It's likely the timing chain that is rattling and making noise because of low oil pressure.

It's not completely unheard of, to have the timing chain wear out on later model 22REs with less than 100K miles, so don't completely rule it out. While the guides may still be in place and appear fine, the chain itself could be stretched out of spec and will still rattle upon start up.

If the OEM filter doesn't work, try using 10w-30 or 10w-40 as was suggested. If that doesn't work, then you may still need to replace the timing chain in the relatively near future. But the fact that the oil pressure stays on is probably the key to the problem here, which would make it oil filter, oil type, or oil pump related. And the oil pumps are virtually indestructable.