Carrying weapons is a two-way street for the armed citizen; and LEOs deserve consideration in the mix.

Michigan law, if one has no CCW permit, is (from MSP FAQ):

1. If I do not have a CCW permit, may I transport my pistol in a motor vehicle?

MCL 750.231a A person is now permitted to transport a pistol for a lawful purpose if the owner or occupant of the vehicle is the registered owner of the firearm and the pistol is unloaded and in a closed case in the trunk of the vehicle. If the vehicle does not have a trunk, the pistol may be in the passenger compartment of the vehicle unloaded and inaccessible to the occupants of the vehicle.
A 'lawful purpose' includes:

While en route to or from a hunting or target shooting area.

While transporting a pistol to or from home or place of business and a place of repair.

While moving goods from one place of residence or business to another place of residence or business.

While transporting a licensed pistol to or from a law enforcement agency for the purpose of having a safety inspection performed (registering the pistol) or to have a law enforcement official take possession of the pistol.

While en route to or from home or place of business to a gun show or place of purchase or sale.

While en route to or from home to a public shooting facility or land where the discharge of firearms is permitted.

While en route to or from home to private property where the pistol is to be used as permitted by law, rule, regulation, or local ordinance.
If you live in a relatively safe area (as I do, where car jacking is not a real threat), carrying an accessible weapon in the passenger compartment (even with a CCW) may be more hastle than it's worth. If I'm going to carry anything in my vehicle, it would be a rifle or shotgun in the trunk. Home and office are a little different story.

Regards

Mike