Maybe you can place your phone somewhere with a better view to the sky so that Strava doesn't recognize that often pauses due to a lack of GPS reception. The auto pause itself can be turned off too for rides (it's a setting in the recording screen before the recording starts) but that would not necessarily add any distance.

I recommend always turning off Auto-Pause. Strava automatically calculates moving time, idle time, and elapsed time along with moving average and other similar calculated stats. With this, as Jan mentioned, Strava won't assume your are stopped simply because you don't have proper GPS signal, or if you are going up a really steep hill and it only seems like you are stopped. As mentioned, you can turn off Auto-Pause by clicking the settings from the Record screen (on Android, this is a gear icon in the top right corner). Tap Auto-Pause, then de-select Bike and/or run.