Leaderboard

Somewhere in the handbook it will tell you about eco mode. Generally the time taken for it to come on depends on how well the battery is charged, so if it is only after a few seconds rather than up to about 15 to 30 minutes then I would be checking the battery voltage. At 7 years old if still the original battery, it could be due for replacing. Whilst on the forum, have a look at the C5 Technical section - there is a pinned topic on Common Problems worth looking at and give you a few other things to check.

The car has gone into "Eco" mode. This is reset by starting the engine. When you try to close the boot with the button and it refuses does it beep twice? If it does this would confirm "Eco" mode to protect the battery. When you turn on the igntion before starting you'll get Eco mode confirmed on the dash.

Welcome to the forum. This is only a guess but possibly the battery is not fully charged. Use a meter to check its voltage, should be about 12.5 volts before the engine is run and about 14.4 volts with the engine running.