imac 2020 keeps waking up every 10 mins!

hi.

I have a bit of a problem with my new iMac 2020 when its asleep it wakes up every 10 mins and I don't know why.

I have power nap enabled which I know will wake up the Mac, I disabled wake for network access but looking at the pmset -g log it shows this.

Currently in use:

 standby              1

 Sleep On Power Button 1

 womp                 0

 halfdim              1

 hibernatefile        /var/vm/sleepimage

 proximitywake        1

 powernap             1

 gpuswitch            2

 networkoversleep     0

 autorestart          0

 standbydelayhigh     86400

 sleep                1 (sleep prevented by sharingd)

 hibernatemode        3

 disksleep            10

 ttyskeepawake        1

 displaysleep         10

 tcpkeepalive         1

 highstandbythreshold 50

 standbydelaylow      86400

incidentally I do not having any sharing items in the sharing preferences turned on.

I have done a pmset -g assertions and I got this.

Assertion status system-wide:

   BackgroundTask                 0

   ApplePushServiceTask           0

   UserIsActive                   1

   PreventUserIdleDisplaySleep    0

   PreventSystemSleep             0

   ExternalMedia                  1

   PreventUserIdleSystemSleep     1

   NetworkClientActive            0

Listed by owning process:

   pid 458(sharingd): [0x0000436400019e6d] 00:07:04 PreventUserIdleSystemSleep named: "Handoff"  

   pid 145(WindowServer): [0x0000409700099d41] 00:00:00 UserIsActive named: "com.apple.iohideventsystem.queue.tickle serviceID:1000006a5 name:AppleHIDKeyboardEve product:Magic Keyboard eventType:3"  

Timeout will fire in 600 secs Action=TimeoutActionRelease

   pid 83(powerd): [0x0000000200088002] 15:05:22 ExternalMedia named: "com.apple.powermanagement.externalmediamounted"  

Kernel Assertions: 0x28=BT-HID,THNDR

   id=500  level=255 0x20=THNDR mod=27/07/2021, 11:13 description=NHI0 owner=AppleThunderboltHAL

   id=505  level=255 0x8=BT-HID creat=26/07/2021, 20:34 description=com.apple.driver.IOBluetoothHIDDriver owner=AppleHSBluetoothDevice

   id=506  level=255 0x8=BT-HID creat=26/07/2021, 20:25 description=com.apple.driver.IOBluetoothHIDDriver owner=AppleHSBluetoothDevice

Idle sleep preventers: IODisplayWrangler

Do you think my external time machine backup disk is causing the iMac to wake up every 10 mins?

Many thanks.