Be sure to test a scooter before you buy it!
If you are losing upper body strength, a scooter that disassembles might not work for you. The battery pack often weighs more than 35 pounds, and you will have to lift it into and out of the car. Make sure there is really enough room in the trunk or your back seat for the largest part of the disassembled unit.
Also, considering your center of gravity is probably pretty high, you want a sturdy scooter so you won't tip over. Again, that adds to the weight issue. Another concern is how much you weigh because that affects the battery life. The more the scooter has to carry, the more often you'll have to recharge it.
Test both three- and four-wheel versions. Whenever you need to go over uneven surfaces like grass or gravel, your choice makes a big difference in how safe you feel. I'm short and slim, but I've tipped my three-wheel scooter more than once. Some have ground clearance of less than 3 inches, and the threshold of a door might actually be high enough that you get stuck.
Consider a bigger scooter if you can. More power, safer, etc. I have a Honda CRV and a lift in the back. My Golden scooter weighs about 140 pounds and I can get it loaded in less than two minutes. It's inside the car so it stays dry regardless of the weather. It takes up all the room behind the second row of seats, but that's ok for us. If you buy a new car, have it checked out thoroughly to be sure that it can accommodate a lift. Most car companies will refund $1000 if you send them a copy of the invoice for the installation of a lift.
I use an Armstrong lift which is actually more expensive than my scooter, but it's worth every penny. It's a sturdy unit, fast and easy to use. Best of all, it mounts to my car's side wall so I can get to the spare tire under the floor if I need to. A floor mounted unit might be bolted in so you can't get to your spare tire.
Another benefit is that it can be completely removed with the unlocking of a couple of mechanisms, so if you don't need the scooter, you can still use the back of the car to carry lots of cargo.
Finally, all this stuff isn't cheap, but you can probably write it off of your taxes.