Continued problems with dropping wifi

For the past several months my wifi will drop randomly throughout the day. Happens on my phone, laptop etc. It will reconnect minutes later. When I check my xfinity app wifi connections I  am able to see that my extender pods( xfinity first gen pods) will have a weak signal. Usually more than one but sometimes just one or the other. 
When it reconnects minutes later everything has a strong signal. 
What could be causing this? Why would the signal be fluctuating like this. It’s so frustrating. 
Can someone help explain what to do. 
I’ve switched out the modems. No help. Reset modems and pods multiple times. 
This seems to be recent problem in past couple months.