When a couple’s relationship is stressed, often there is a reduction in caring behaviours — verbal or non-verbal expressions of interest, respect, concern, and affection. Both partners are likely waiting for good feelings to return before acting positively towards each other. An effective way to jump start the relationship is to consciously increase the rate of exchange of caring behaviours. This may seem unnatural at first, but good feelings will grow from the experiences created by these positive actions.
This link from Psychology Today offers some ideas on this topic: