Data loss after restart

Device is Samsung Galaxy Tab A 7.0 (2016) 4G LTE (SM-T285), running Android 5.1.1 (Lollipop), without root.

Device suddenly lost network coverage (not the first time), and flight mode did not solve it (not the first time, also), and the only way usually was to restart (power off/on).

Usually that would solve the problem.

This time, the same thing happened, and upon restarting the device, it spent a long time at the Samsung logo/splash screen (which is abnormal), and when it finally reached the lock screen, it took a while before the entire screen was loaded (wallpaper appeared first, then the time...). Upon entering into the home screen, some (not all) widgets were missing (noticeably the custom downloaded ones).

Opened the usual apps to pick up from where I left off, and those apps ran as though it was the first time (as if it was just installed). App data (that was stored on internal storage) was lost. Other data (SMS, pictures) were intact.

My immediate concern/focus right now is to recover the lost data, either by fixing this abnormality (safe mode/guest mode, maybe?), and if that fails, at least recover the lost data (preferably without requiring root).

Any ideas?

Any ideas?