Hi Stevo44,
The kind of “roll together” that you are experiencing in the middle of the mattress when two people are “spooning” or sleep closer together isn’t an uncommon complaint with softer mattresses that have either softer support cores or thicker and softer comfort layers. There are also some comments about firmer foam edge support with innersprings in post #2 here and your experience here also isn’t unusual.
There is little you can do about the firmer edges but some of the suggestions in post #4 here may be “somewhat helpful” for the softer areas in the middle. In most cases though … choosing a mattress where you are less likely to experience this in the first place is a more effective approach than trying to “fix it” afterwards because you can always soften up a mattress that is too firm by adding a topper but it’s much more difficult to firm up a mattress that is too soft or that is sagging because this would generally involve removing and replacing layers rather than adding layers on top of the mattress.
Phoenix