Mu guess is because of moderate daily volumes (summer), and larger share blocks coming up over the course of the day. Check out the order book to see if a block greater than 10,000 shares is up for bid. That'll torque the transactions either up or down as the larger block soaks up the 100, 200, 400 bid/asks. This stays very volatile until news is released. Then it spikes up...or down. Best of luck to you. Disclosure: I'll add to position below 4.10. Otherwise I hold current share levels. Long.