Leaving frozen hamburger patties in a freezer bag in a car is not recommended as it can lead to temperature fluctuations and potential food safety issues. When frozen food thaws and then refreezes, it can encourage the growth of harmful bacteria, which can cause foodborne illnesses when consumed.
The fact that the edges of the hamburger patties have become soft indicates that they have likely started to thaw. Once the edges have softened, the quality and safety of the meat may have been compromised.
It is not advisable to refreeze the hamburger patties at this point. Doing so would not kill any bacteria that may have grown during the thawing process. As a general rule, it is safer to cook the patties immediately after they have started to thaw. If you're unsure about the safety of the patties, it's best to discard them to avoid any potential health risks.
To prevent food safety issues in the future, always try to transport frozen food in a well-insulated cooler with ice packs or keep it in a freezer until you are ready to cook or consume it. This helps maintain a consistent and safe temperature for the food.