The latest reported incidents took place on Le Frie Baton and Le Courtil Michele in St Saviours early on Wednesday morning.
Guernsey Police say they are particularly interested in speaking to anyone with a dash cam or CCTV footage, in particular any footage from around 03:00.
In a statement a spokesperson said: “Unfortunately, this serves as a timely reminder for vehicles island wide to be kept locked when not in use and for any valuables to be removed overnight.”
Anyone with information or potentially helpful footage, is asked to contact PC 97 Du Port or PC 55 Le Bachelet on 22222 or anonymously through Crimestoppers.