Timeline preview render issue

Hi,
if I had put a transition or any other effect on my current timeline resolve started automaticly a render process for that particular area of my timeline.

But now it doesn't. Maybe I switched it of by mistake. However it doesn't work anymore and I have no idea how I can fix that.

Are there anyone who can help?

Thanks
inetd1910

Read up on the Cache settings. Part 2 of the User Manual, section titled Improving Performance, Proxies, and the Render Cache

Thank you for your helpful answer.