Recently I had to reinstall the the software again, but this time I was careful about not launching it more than once at a time - previously I mentioned that I suspected that the failure was caused by launching the program and opening a new workspace at the time when the program was already running. But anyway, after a while the problem appeared again: the program didn't wanted to start up.
I didn't want to reinstall it again, instead I tried to modify the files in the installation folder. I don't know how, but the following solved my problem:
in C:\NXP\S32DS_ARM_v2018.R1\eclipse\configuration\.settings I opened the org.eclipse.ui.ide file with note pad, and rewrote the second line in it as follows:
RECENT_WORKSPACES=\\
After that, the program did start up. I searched the workspace location in which I've been working before, it loaded and it seems that everything is working fine now.