Is it just my kids or is it common?

As long as I am upright and moving around, my kids are in general happy to play/potter around and do their own thing. It doesn't matter if I'm sorting washing, doing gardening, cleaning or cooking. BUT...the moment I sit down still to do something or lie down for a bit of a rest, they are climbing all over me, whinging and bugging me (well Joanna more so than Ben these days).