Short answer: If a protective device trips repeatedly, avoid continually resetting it. Note what was running, whether the trip is immediate or delayed, and whether one circuit or the whole property is affected.
What can be involved.
A connected appliance
A faulty appliance can cause a protective device to operate when it is connected or switched on.
A circuit fault
Damage, moisture or another electrical fault on a circuit can cause repeated trips.
An intermittent condition
Some faults only appear under load, in damp conditions or at particular times.
More than one issue
Older or modified installations can have multiple contributing problems, so diagnosis matters.
Safety note: This guide is general information, not DIY electrical instructions. Electrical testing, repairs and alterations should be carried out by an appropriately licensed electrician.