How is an automotive battery assembled?

Yes

It is a storage cell for electricity. The starter needs a burst of electricity to start the motor. Then, after that, it is used primarily for bursts, and storage. Let's talk tech, here for a minute....

Series.

When your car is having trouble starting up or when you turn it up and you notice it struggling a little

that would be due to the battery overheating, possibly caused by overcharging.