unattended-upgrade taking a lot of CPU power

I've recently upgraded my OS from Ubuntu 16 LTS to Ubuntu 18.04 LTS and it's been a few days that the process unattended-upgrade is taking a lot of CPU power, forcing my fan to be quite noisy (cf screenshot)

Do you know what this process do, why it is always running and why it is so greedy in terms of CPU power? (What could it be possibly doing with all this calculation power?) Is it safe shutting it down?

Many thanks in advance for your help! :-)

EDIT: I tried to upgrade apt-get and i got the following message:

E: Could not get lock /var/lib/dpkg/lock-frontend - open (11: Resource temporarily unavailable)
E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), is another process using it?

Can't use sudo anymore, could unattended-process be using sudo? if so why for so long?