Weird Action

Why does my Syma X5c-1 all of sudden start flipping by itself with no input?

Hi mate it can be as simple as a bad connection the transmitters

Could be the gimbal stick Is kuput.
The fcb/esc is dodgy & picking something up causing a signal. Had a heavy crash recently. These toys don't last long especially the brushed motors. They should all come with spares. In my experience to buy separate or spare parts can be just as expensive as the drone itself.