If your scooter starts beeping after holding the throttle down for a few seconds it is likely that cruise control is turned on. Cruise control is a P1 setting and can be turned on and off through display menu. If Cruise control is on then the scooter will maintain its current speed after you release the throttle. You can see how to turn this function on and off here.
If cruise control is not turned on, this is likely due to a battery or battery connection issue. Please check out our Battery section in Trouble Shooting / Maintenance.