I couldn't find anything on the Swagtron G7, but the way a lot of eBikes work is that they have a cadence sensor. When the bike senses you're pedaling, it immediately accelerates you to the speed dictated by whatever PAS (Power Assist System) setting you've chosen. PAS level 1 may be 8 or 9 mph, so if for example you're pedaling in a low gear that would take you to 6 mph if the electric system weren't on, it is surpassed immediately.
If you shift the mechanical gears up to something higher, you can pedal to assist the electric motor.
Is it possible you're turning the throttle a bit without noticing? Many eBikes will then use the motor regardless of your pedaling.
On that bike, you'll have to get used to how that works. If you find it really disconcerting, sell it and get an eBike with a torque sensor; those apply power in proportion to your own supplied torque and feel more natural. They have no relation to speed, except that they will stop providing electric power at a certain top speed. In the USA, this is either 20 mph (Class 1 or 2) or 28 mph. (Class 3) Outside the USA, it is usually 25 kph (15.5 mph).