my 9020 just did the same after putting in storage for a while, previously working fine.  The easiest quick fix is to clear cmos settings via motherboard jumper RTCRST.  I think these pc have a dying cmos battery which cannot hold nonvolatile memory well. The battery may not be quite dead but is getting old thus the rom is losing memory kind of like getting demented.  If clear cmos fixes problem, replace cmos battery with a brand new one at your earliest convenience.
Hi, I have an OptiPlex 3020 SFF that turns on and before post and without video image shuts down in about 2 seconds, I have checked power cable and it checks ok, the CPU fan spins at the initial power on so the fan is ok, I have taken out the CD drive and hard drive to eliminate a short and it does the same, unless there is something common in this model I am going to assume it's either the power supply or the motherboard, can anyone assist me in this ?Thank You for your time.
Optiplex 3020 SFF turns on then off