##原因：対応したKernelイメージがインストールされていない

sudo -i
#ユーザーパスワードを入力
~# /sbin/vboxconfig 
vboxdrv.sh: Stopping VirtualBox services.
vboxdrv.sh: Building VirtualBox kernel modules.
This system is currently not set up to build kernel modules.
Please install the Linux kernel "header" files matching the current kernel
for adding new hardware support to the system.
The distribution packages containing the headers are probably:
    linux-headers-generic linux-headers-4.15.0-24-generic
This system is currently not set up to build kernel modules.
Please install the Linux kernel "header" files matching the current kernel
for adding new hardware support to the system.
The distribution packages containing the headers are probably:
    linux-headers-generic linux-headers-4.15.0-24-generic

There were problems setting up VirtualBox.  To re-start the set-up process, run
  /sbin/vboxconfig
as root.

Linuxカーネルヘッダがインストールされていないとのこと。おすすめされたlinux-headers-4.15.0-24-genericをapt installします。

apt install linux-headers-4.15.0-24-generic -y

再び/sbin/vboxconfigを実行する

~# /sbin/vboxconfig 
vboxdrv.sh: Stopping VirtualBox services.
vboxdrv.sh: Building VirtualBox kernel modules.
vboxdrv.sh: Starting VirtualBox services.

無事にセットアップできました。