This was a 1970s short story, which has something in common with Damon Knight's classic "Four in One".
Random individuals on Earth start to dissolve into pools of protoplasm. This naturally gives the impression that some hostile alien has eaten them, leading to violent reactions. However if the blobs were given food and shelter for a few weeks, they re-formed into next-generation humans.
I recall that in one case, somebody tried putting the protoplasm of his nearest and dearest into a sort of human-shaped jelly mould, but it wasn't necessary.