To my ears, this has gained in currency in the past 5 years or so. Listen to interviews on TV and the Radio, how many time do you hear it? (Melvin Bragg on Kepler (Radio 4) this morning - one person used it almost every time he opened his mouth.)
Typically, it is uttered by an 'expert' on some matter or other - typically academic or technical.
It's a useful device. It makes it appear that the listener has listened to and fully understood the interlocutor so that what s/he is about to say fully responds to the previous statement - rather like the german, 'Also', meaning 'thus'.
Do you find yourself using this? When did it start? Where did it come from?
Or is it, like the use of the word 'invite' instead of 'invitation', an older English useage which has return to favour?
(No points at all to the person who starts the next post, "So...")
