There is no automated reboot available within the Meraki dashboard, so it's not that.
It could be several things
1. Your ISP/Internet is losing connection briefly, when this happens, you see those AP's losing their cloud connection, but are still technically 'up' and running.
2. If they are on the same switch, its possible that switch, or one further up, is losing Internet access, rebooting etc.
I would contact support and ask them what the UPTIME is for the access points. That will tell you more information. If they are not rebooting, then its most likely your WAN connection.
I would also suggest you upgrade your firmware to 26.8.1