Check your accessibility settings and see if readout is checked. Our something along those lines. Does it say anything else? With readout checked it should read on-screen prompts as well as notifications. This could also be a feature of some other app associated either with notifications or caller id. So if you've installed a launcher or caller id app there may be a setting in there that needs fixed.
Old style phones used to have, car mode. In car mode it reads out notifications and caller id info for the driver so they don't have to look at the device. Check your device settings for this also if you find that readout is not checked in your accessibility settings.