Animation sequence pauses

Hi

I have a slide where 4 text captions appear in sequence then a line and oval shape following in sequence.

If I play the slide from the timeline the sequence is OK.

When I preview the slide- the four captions appear in sequence OK but then the piece pauses and I have to click the play button in the in the playback bar to start the rest of the sequence.

I can't figure out why it pauses or find a control to amend it.

Help appreciated

Thanks