This is probably due to the automatic Unpaid Item Assistant. If you want to start it after 2 or more days you need to update your combined payments preference to reduce the timescale (it's where buyers can only combine payment for items purchased within a certain number of days, eg. 3 days. If longer it prevents UIA starting until that timescale is up).
To do that go to My eBay > Account tab > Site Preferences > Postage and packaging preferences > Show > Offer Combined Payments and Postage > Edit.
