The battery is beneath the passenger footwell
Check the Negative (-) terminal clamp is tight
Check the Positive (+) terminal clamp is tight. CAUTION If using a spanner to tighten terminal, be careful not to short it on the bodywork. Replace cover
Check battery is generally secure, if loose, tighten the battery retainer. Tighten if required, a 13mm socket is needed. Not too tight as you may damage the battery casing