Also definitely change this setting, it has been mentioned so many times by people having the same problem in Chrome, Edge, Opera etc browsers as they are all based on Chrome.
Type the following into the Address Bar: chrome://flags/#calculate-native-win-occlusion
Change the setting to Disabled
In a reply you said "The second suggestion isn't a problem as my tabs line up beside each other and not on top of each other."
The setting is happening if a screen saver comes on, you minimise the window, another window is in front, and also sleep.