2000 Yukon loses gear after a mile or so

So my 2000 Yukon starts and rpms are good. I let
it sit for awhile then turn it on I can drive a mile or
sometimes more but then I lose gear. So I let it sit
a few mins then I can start it again and go. I’m not
sure when the last time it’s filter has been
changed. I bought it with almost 300,000 miles just
for a work truck. I’m not sure if it just needs a new
filter and fluid or what to do. There are no codes or
engine and transmission lights popping up.