Thematic root aorist

Hi!

Is there any PIE root that is by itself a thematic root
aorist/punctual, in the same way as *bher- is durative?

The best example I did find for now is from Vedic ávidam / ávidas /
ávidat, but this verb seems to be from our old friend *weyd-. If so,
from where came the -n- from the present vindá:mi / vindási / vindáti?
Is that the nasal infix from the seventh class, that went to the weak
grade as it lost the accent for the thematic vowel, or am I just messing
up everything ; )?

Edgard.