O2 sensor failure???

[lexus95]

I have 95' LS400 with air suspension. Recently, it happened to me twice while I was driving under normal condition for about 5 to 10 min and suddenly my LS400 engine has the symptom of O2 sensor(s) failure but the check engine light was not on. I turned off engine for about 30 min then turned back on. The engine was normal to drive again. Any ideas which sensors or parts went wrong? Thanks.