Undo the splashshield in the front wheelwell
This is where your battery is located
Check the Negative (-) terminal clamp is tight and if necessary, tighten
Check the Positive (+) terminal clamp is tight. CAUTION If using a spanner to tighten terminal, be careful not to short the spanner on the bodywork
Check battery is generally secure, if loose, tighten the battery retainer bolt at the top of the battery. . .
. . . then tighten the bolt at the bottom of the battery. Not too tight as you may damage the battery casing