Sorry to hear that! My two thoughts on what could be causing this:
- A issue similar to that of what is known to be experienced by LIGHTIFY bulbs (and similar models) where they “turn on” randomly because the bulb software crashes, the light reboots, and then returns to an “ON” state after the reboot. These Community posts cover that phenomenon: Osram Lightify Smart Bulbs Randomly Turning On / OSRAM LIGHTIFY Light turning on by itself (there are definitely more examples out there).
- The Switch you have these bulbs attached to cannot support the load of all the lights. This you’d have to check on yourself and I am by no means an electrician.
I’m pretty confident though these bulbs are losing power or rebooting, as they do return to an “ON” state when that happens. I use Sengled bulbs as well for a few lamps in my house and can attest to that they do that when power cycled, although I’ve never had the specific issue you describe with them. Hope this is helpful!