I can't even take a guess as to why your vibration functionality is missing after just restarting your phone but have you checked in your Settings menu to see if anything is enabled or not? You might want to just toggle them and then later do another restart just to confirm there still enabled. On one of my phones the options are sometimes in categories that seem a bit odd or buried deep in some sub-menu of another menu -- i.e. Settings >> Languages & input >> Virtual keyboard >> Gboard >> Preferences while another is in Settings >> Sound >> Other sounds
If your settings changes are still held after rebooting than that previous problem might have been just a one-off matter. If not though, that could be a serious problem.
Sorry,not a very solid reply, hopefully others will comment with more substantive suggestions.