My '93 4/4 had a starting slow turnover. It was the earth connections plus an aged battery. I checked and changed the battery but still slow turning over. New earth straps front and rear, cleaned connections to starter motor. Problem gone.
If you think about a Morgan not many do high miles and tend to be kept long term in a garage/ elsewhere.
Time can be your enemy as things age deterioration can occur. Exposed wiring, bullet connectors ( why?) corrode, insulation hardens and cracks etc.
Similar with other systems. Fuel pipes, filters, pump etc. Interior wear and tear, corrosion......
Annual servicing including a "spanner check" is ok BUT occasional in depth inspection of wiring, pipework, etc is needed. Think about the extra servicing checks/ jobs on the schedule as age/ mileage increase.
DaveW was the master of this! Me? A lesser bersion but enjoyed most of the work.
My 20 yr old Plus 8 had 74k miles when part ex'd for a Plus Four. I had a list of checks/jobs to do IF I was going to keep it, basically future proofing stuff before issues occured. I had already done some wiring refurb when faults were found and repaired, adding that little bit extra upgrade as part of the repair. Add in mods to improve on the MMC assembly methods!
All part of the hands-on Morgan ownership fun.