IE 11 F12 developer tools unresponsive

Recently, as in the last couple of weeks, IE 11 F12 developer tools have become unresponsive. Not totally, but it is so sluggish as to be almost useless. I will see the window open after a while, but it is still hidden behind the browser. Clicking on it does not give it the focus. Finally, it will come get the focus, but then, clicking on any tab takes forever to switch. I can switch away from it back to IE normally while this is happening, and IE is totally responsive. Even clicking the Select Element on the DOM Explorer can take 30 or more seconds before it switches back to IE for me to select. Note that this behavior is not consistent; sometimes it is as responsive as ever. I haven't installed any new software recently (other than Windows updates). Windows 10 Professional 64-bit version 1803, AMD FX8350 8-core CPU 4.0GHz, 16GB RAM, Crucial 512GB SSD, WD 1TB 10000 RPM HDD, IE 11.48.17134.0, OneNote and Java are the only extensions/add-ons enabled.