Yes you can trade them as you like up to the 9.9k limit and as often as you like and move from cash to etfs and back within the sipp. So yes every week is fine, there is no minimum term for holding them as they are exchange traded just like stocks really but without stamp duty. Try a small trade to see.
There is a minimum term on the SIPP of course, you can’t withdraw till you retire, so it’s for very long term savings only as it is a pension but that’s probably not what you’re asking.