Every time you add a button, click box, shape used as a button or image used as a button the default is to add a pause after 1.5 seconds into the button’s appearance to allow your learner time to press button. However, you can navigate to the Timing panel for that interactive object and turn off the pause by de-selecting it.

To answer your question more details are wanted. Never forget to mention the exact version you are using (full version number is under Help, About Captivate).

There are many Preview methods, which one did you use? If you are busy with a non-responsive project, the most to be trusted preview is F11, Preview HTML in browser.  For responsive projects this is less important. However the ‘Play slide’ which is mentioned under the Preview button is NOT a preview method at all. The used browser can also be relevant because not all browsers support all features.

You talk about ‘pauses’. Did you check the Timeline panel? Most pauses, but not all, will be visible on the timeline. Read more about pausing the timeline in this blog post:

http://blog.lilybiri.com/pausing-captivates-timeline