No, if you can afford to pay annually in one lump sum, you’ll normally find you save money on your car insurance.
There are pros and cons to either paying your car insurance annually or monthly. Monthly payments spread the cost of your car insurance, which can be useful, but you’ll usually end up paying more overall as the insurance provider will charge interest.  If you can only afford (or need) insurance for part of the year, consider temporary car insurance. But you’ll usually find this is more expensive compared to a monthly rate. Having temporary cover will also prevent you building up a no-claims discount.