Vanadium dioxide (VO2) devices undergo an insulator-metal-transition by current or voltage injection. This resistive switch is of interest for the implementation of cutting edge applications in high-speed electronics and neuromorphic computing. The use of commercial TCAD software tools to simulate VO2 devices can boost their industrial exploitation. Unfortunately, physical models able to capture the complex physics of VO2 material are currently unavailable in TCAD tools. In this work, we utilize a dedicated TCAD modeling approach to simulate thermal-induced resistive switching effects in VO2 devices. We report on 3D electrothermal simulations by a commercial TCAD software tool. Moreover, we confirm that the Joule heating effect is indeed the underpinning mechanism to explain all the main features in the current vs. voltage curves of VO2 devices. Finally, we present 3D TCAD electrothermal simulations of a relaxation oscillator based on a VO2 device and report on device self-oscillatory behavior due to voltage and temperature.