Painfully slow website after migration to live server

For some unknown reason all the websites I’ve build become painfully slow when uploaded to live server. I used different themes (the7, woodmart, fox) and they’re all balzing fast inside flywheel but when migrated to live environment they slow down so much they become unusable. I use backupbuddy to move the whole installation from flywheel to ftp directory. Not sure what’s causing the sloweness and how to trace it.
Wonder if anybody had the same issue?